True Televisions have the CRT Tube !!
Welcome to the Obsolete Technology Tellye Web Museum. Here you will see a TV Museum showing many Old Tube Television sets
all with the CRT Tube, B/W ,color, Digital, and 100HZ Scan rate, Tubes technology. This is the opportunity on the WEB to see, one more time, what real technology WAS ! In the mean time watch some crappy lcd picture around shop centers (but don't buy them, or money lost, they're already broken when new) !!!

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and information about some of the electronic, electrical and electrotechnical technology relics that the Frank Sharp Private museum has accumulated over the years .

Premise: There are lots of vintage electrical and electronic items that have not survived well or even completely disappeared and forgotten.

Or are not being collected nowadays in proportion to their significance or prevalence in their heyday, this is bad and the main part of the death land. The heavy, ugly sarcophagus; models with few endearing qualities, devices that have some over-riding disadvantage to ownership such as heavy weight,toxicity or inflated value when dismantled, tend to be under-represented by all but the most comprehensive collections and museums. They get relegated to the bottom of the wants list, derided as 'more trouble than they are worth', or just forgotten entirely. As a result, I started to notice gaps in the current representation of the history of electronic and electrical technology to the interested member of the public.

Following this idea around a bit, convinced me that a collection of the peculiar alone could not hope to survive on its own merits, but a museum that gave equal display space to the popular and the unpopular, would bring things to the attention of the average person that he has previously passed by or been shielded from. It's a matter of culture. From this, the Obsolete Technology Tellye Web Museum concept developed and all my other things too. It's an open platform for all electrical Electronic TV technology to have its few, but NOT last, moments of fame in a working, hand-on environment. We'll never own Colossus or Faraday's first transformer, but I can show things that you can't see at the Science Museum, and let you play with things that the Smithsonian can't allow people to touch, because my remit is different.

There was a society once that was the polar opposite of our disposable, junk society. A whole nation was built on the idea of placing quality before quantity in all things. The goal was not “more and newer,” but “better and higher" .This attitude was reflected not only in the manufacturing of material goods, but also in the realms of art and architecture, as well as in the social fabric of everyday life. The goal was for each new cohort of children to stand on a higher level than the preceding cohort: they were to be healthier, stronger, more intelligent, and more vibrant in every way.

The society that prioritized human, social and material quality is a Winner. Truly, it is the high point of all Western civilization. Consequently, its defeat meant the defeat of civilization itself.

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

OLD, but ORIGINAL, Well made, Funny, Not remotely controlled............. and not Made in CHINA.

How to use the site:

- If you landed here via any Search Engine, you will get what you searched for and you can search more using the search this blog feature provided by Google. You can visit more posts scrolling the left blog archive of all posts of the month/year,or you can click on the main photo-page to start from the main page. Doing so it starts from the most recent post to the older post simple clicking on the Older Post button on the bottom of each page after reading , post after post.

You can even visit all posts, time to time, when reaching the bottom end of each page and click on the Older Post button.

- If you arrived here at the main page via bookmark you can visit all the site scrolling the left blog archive of all posts of the month/year pointing were you want , or more simple You can even visit all blog posts, from newer to older, clicking at the end of each bottom page on the Older Post button.So you can see all the blog/site content surfing all pages in it.

- The search this blog feature provided by Google is a real search engine. If you're pointing particular things it will search IT for you; or you can place a brand name in the search query at your choice and visit all results page by page. It's useful since the content of the site is very large.

Note that if you don't find what you searched for, try it after a period of time; the site is a never ending job !

Every CRT Television saved let revive knowledge, thoughts, moments of the past life which will never return again.........

Many contemporary "televisions" (more correctly named as displays) would not have this level of staying power, many would ware out or require major services within just five years or less and of course, there is that perennial bug bear of planned obsolescence where components are deliberately designed to fail and, or manufactured with limited edition specificities..... and without considering........picture......sound........quality........

Wednesday, September 14, 2011

30AX
is a new in-line color TV display system with 110
deflection angle and interchangeable tubes and yokes.
It is based on the production experience gained
with the 20AX system introduced in 19741,2,3) and the
results of further investigation in the field of tube
technology and deflection yoke design. For the tube, this
meant a new reference system, an internal magnetic
correction ring and an improved gun design. For the
yoke, the most important elements are a new
"flangeless" winding technology, a change in the shape of
the windings at the screen side of the line deflection
coil and the use of field shapers embedded in the
deflection coil.

A deflector for a
cathode ray tube (called herein "CRT"), and more
particularly a stator type deflector in which a
plurality of slots for windings are formed in the inner
surface of a tubular core and deflecting coils are
positioned in these slots.

The deflection Joke is a HIGH PRECISION MONO TOROIDAL TYPE.

PHILIPS 30AX SYSTEM BACKGROUND OF THE INVENTION

This
invention relates to self-converging color picture
tube or kinescope display systems that do not
require precise transverse, or tilt, alignment
between the deflection yoke and the electron beams of
the kinescope.

Color
television kinescopes or picture tubes create color
images by causing electrons to impinge upon
phosphors having different-wavelength emissions.
Normally, phosphors having red, green and blue-light
emission are used, grouped into trios or triads of
phosphor areas, with each triad containing one phosphor
area of each of the three colors.

In
the kinescope, the phosphors of each of the three
colors are excited by an electron beam which is
intended to impinge upon phosphors emitting only one
color. Thus, each electron beam may be identified by
the color emitted by the phosphor which the beam is
intended to excite. The area impinged on by each electron
beam is relatively large compared with a phosphor
triad, and at any position on the screen, each beam
excites a particular color phosphor in each of several
triads. The three electron beams are generated by three
electron guns located in a neck portion of the
kinescope opposite the viewing screen formed by the
phosphors. The electron guns are oriented so that the
undeflected beams leave the gun assembly in converging
paths directed towards the viewing screen. For the
viewing screen to display a faithful color reproduction
of a scene it is necessary that the beam position
relative to the kinescope be adjusted for producing color
purity and static beam convergence at the center of
the screen. The purity adjustment involves causing
each of the red, green and blue beams to excite only
its respective phosphor. This is accomplished by the
shadow mask. The shadow mask is a screen or grill having
large numbers of perforations through which the electron
beams may pass. Each perforation is in a fixed
position relative to each triad of color phosphor
areas. The electron beams pass through one or more of the
perforations and fall upon the appropriate color
phosphors based upon their directions of incidence. Color
purity depends upon a high order of accuracy in the
placement of the phosphor triads relative to the
perforations and the apparent source of the electron beams.

Static
convergence involves causing the three beams to
converge at one scanning spot at or near the center of
the viewing screen. Convergence at the center of the
screen may be accomplished by the use of a static
convergence assembly mounted relative to the neck of the
kinescope and adjusted or magnetized to produce a static
magnetic field which causes the three beams to
converge at the center of the viewing screen.

In
order to form a two-dimensional image, the
luminescent spot excited on the viewing screen by the
three converged electron beams must be scanned both
horizontally and vertically over the viewing screen to
form a luminescent raster area. This is accomplished by
means of magnetic fields produced by a deflection
yoke mounted upon the neck of the kinescope. The
deflection yoke deflects the electron beams with
substantially independent horizontal and vertical
deflection systems. Horizontal deflection of the
electron beams is provided by coils of the yoke which
produce a magnetic field having mainly
vertically-directed field lines. The magnetic field
intensity is varied with time at a relatively high
rate. Vertical deflection of the electron beams is
accomplished by coils producing mainly a
horizontally-directed magnetic field which varies with time
at a relatively low rate. A permeable magnetic core is
associated with the yoke coils. The conductors of the
coils may enclose the core to form a toroidal deflection
winding, or the conductors may form saddle coils
which do not enclose the core.

The
kinescope viewing screen is relatively flat. The
electrons of each electron beam will traverse a
greater distance when deflected towards the edge of
the viewing screen than when directed toward the center.
Due to the separation of the electron guns, this may
result in a separation of the landing points of the
three electron beams when near or deflected towards
the edge of the screen. In addition, prior art
almost-uniform magnetic deflection fields caused the electron
beams to be overconverged when deflected away from
the center of the screen. These effects combine to
cause the light spots of the three beams at points on
the viewing screen away from the center to be
separated. This is known as misconvergence and results
in color fringes about the edges of the displayed
images. A certain amount of misconvergence is tolerable,
but complete separation of the three illuminated spots
is generally not acceptable. Misconvergence may be
measured as a separation of the ideally superimposed
red, green and blue lines of a crosshatch pattern of
lines appearing on the screen when an appropriate test
signal is applied to the picture tube. Each of the three
electron beams scans a raster, which may be
identified by its color. Thus, a green raster is
ordinarily scanned by the center electron beam, and the
outside beams scan red and blue rasters. The crosshatch
pattern is formed in each of the red, green and blue
rasters. The crosshatch pattern outlines the raster
with vertical and horizontal lines, and also includes
other vertically and horizontally-directed lines, some
of which pass through the center of the raster.

PHILIPS 30AX Deflection unit for a color television display tube:
A deflection unit for a color television display
tube 1 having a field deflection coil 8 and a line
deflection coil 7, in which the line deflection coil
is formed by two diametrically oppositely positioned
coil portions which, on the side adjacent the tube's
screen, have a flared end 17 having a profile with a path
length 22 which is longer than the path length 23 of
the contour of the outer surface of the tube, so
that raster defects are smaller than when the profile
of the flared ends conforms to the contour of the tube
surface.

1.
A deflection unit for a color television display
tube having a neck portion a display screen and a
partly flared outer surface portion therebetween,
said deflection unit comprising a field deflection coil, a
line deflection coil, each of said deflection coils
being formed by a pair of diametrically oppositely
positioned coil portions, and an annular core of a
magnetically permeable material surrounding at least the
line deflection coil, each line deflection coil portion
being in the form of a saddle coil and having
conductors wound to produce first and second side members, a
front end and a rear end which together define a
window, said front end being in the form of a flange,
the front ends of the coil portions of said line
deflection coil, when said deflection unit is mounted on
a display tube, being closer to the display screen
than are the rear ends, with said front ends substantially
surrounding a part of the flared portion of the
display tube and the plane of the flange-like front
ends being at an angle to the longitudinal axis of said
display tube, and said first and second side members
extending mainly parallel to the tube axis characterized
in that the front ends of the line deflection coil
portions together define a path whose length is greater
than the length of a path around the flared portion of
the display tube at which said front ends are intended
to surround. 2. A deflection unit as claimed in claim
1, characterized in that the front ends of the line
deflection coil portions together define a polygon. 3. A
deflection unit as claimed in claim 2, characterized in
that the polygon is a hexagon. 4. The combination
of a deflection unit as claimed in claim 1, 2 or 3,
and a color television display tube having a neck
portion, a display screen and a flared outer surface
portion therebetween, said deflection unit being mounted
on said display tube such that the front ends of the
line deflection coil portions are closer to the
display screen than are the rear ends, with the said
front ends surrounding a part of the flared portion of
the display tube and the flange-like front ends lying
substantially at right angles to the longitudinal axis
of the display tube, the path length around said
flared portion of said display tube being shorter than
the path length of the front ends of the line
deflection coil portions surrounding said flared
portion, so that defects in a raster formed on the display
screen are smaller than when the said path lengths
are equal.

Description:

BACKGROUND OF THE INVENTION
The
invention relates to a deflection unit for a color
television display tube having a neck portion, a
display screen, and a flared outer surface portion
therebetween, said deflection unit comprising a field
deflection coil and a line deflection coil each formed by a
pair of diametrically oppositely positioned coil
portions, and an annular core of a magnetically permeable
material surrounding at least the line deflection
coil, each line deflection coil portion being in the form
of a saddle coil and having conductors wound to
produce first and second side members, a front end and a
rear end which together define a window, with the front
end forming a flange, the front end of the coil
portions of said line deflection coil, when said
deflection unit is mounted on a display tube, being closer
to the display screen than are the rear ends, with
said front ends substantially surrounding a part of the
flared portion of the display tube and the flanges,
lying at an angle to the longitudinal axis of said
display tube.
Such a deflection unit is commonly
used for deflecting the electron beams in color
television display tubes. In this known unit, the two coil
portions which form the field deflection coil and the
two coil portions which form the line deflection
coil are both adapted, as regards their shape, to the
flared profile of the display tube for which the
deflection unit is destined. This means that the
individual conductors of the coils engage the glass of the
display tube as closely as possible when the
deflection unit is mounted on the display tube for which
it is intended. This applies in particular to the line
deflection coil, since the sensitivity of the line
deflection system is an important parameter with
respect to the quality of a deflection device. For that
purpose it is usual to make the front ends of the coil
portions of the line deflection coil arc-like in shape
such that they closely follow the contour of the
display tube at its flared portion. This contour is
often rotationally symmetrical so that the front ends
in that case are of circular shape.More
rectangular shapes of this contour are also known,
involving a corresponding shape for the front end so
that in that case also they optimally conform to the
contour of the display tube.
Parameters, known so
far which are suitable to spatially shape the magnetic
field of a deflection coil of the saddle type and
which fully satisfy the requirements with respect to
an optimum sensitivity, are provided by the wire
distribution of notably the two substantially axially
extending parts of each coil portion of which parts
the front end forms the connection. Known techniques
for this purpose are profiling of the space in the
winding mould, profiling of the press die and the insertion
of pins in the mould during the winding process.
Furthermore it is known that the shape of the
soft-magnetic core may also be used as a parameter to some
extent.
It is known that in general a color
television display system may present errors which may
be distinguished as coma, astigmatism, raster defects
and linearity defects. For so-called "three in-line
guns" display systems it has proved generally possible,
by using the above-mentioned design parameters, to
make deflection coils by which astigmatism defects are
sufficiently minimised.
Coma can also be
minimised often in a corresponding manner. The situation is
different for the raster defects and the linearity
defects. The raster defects are divided into the
North-South and the East-West defects. In "in-line"
systems the North-South raster defect produces horizontal
lines at the lower and upper edges of the picture which
show a slight undulating distortion, while the
East-West raster defect produces a
strong-pin-cushion-like distortion which may be typically
between 8 and 14%. Corrections for raster defects and
linearity defects are obtained in general by suitable
modulations of the line and field deflection currents.
In addition, static magnets may alternatively be used
for the correction of the undulating distortion.
A
known disadvantage of modulating deflection
currents, however, is that complicated electronic
deflection circuits are required, which moreover consume
additional energy and hence provide an expensive
solution. In addition to a higher cost-price, the
disadvantage of the use of static correction magnets is
that, when the correction has to be larger than a few
mm, problems arise with regard to the color purity.
SUMMARY OF THE INVENTIONIt
is an object of the invention to provide a
deflection unit and a color display tube/deflection
unit combination which reduces at least one of the
above distortions.
According to one aspect of the
invention there is provided a deflection unit as
described in the opening paragraph of this
specification, characterized in that the front ends of
the line deflection coil portions together define a path
whose length is greater than the length of a path around
the flared portion of the display tube at the part
thereof which said front ends are intended to
surround.
The invention also provides a color display tube in combination with a deflection unit as described above.
The
invention is based on the use of a real coil design
parameter by means of which the undulating
distortion and the pin cushion-like East-West raster
defect, respectively, can be favorably influenced,
and is achieved by the shape of the front end of the
line deflection coil being no longer made as short as
possible, as has been usual so far. As a result of
this, the resulting sensitivity of the line deflection
coil is slightly less than in conventional designs
having the shortest possible length of front end, but,
since, compared with designs in which the defects are
removed by means of modulation of the deflection
currents, the modulation becomes less, the electronic
deflection circuits may be simpler which results in a
lower overall energy consumption than that required
with line deflection coils having a minimum front end
length. The simplification of the circuits and their
lower overall energy consumption both result in a lower
cost-price. When, for the correction of any remaining
"undulation effect," a static magnet is required, a
weaker magnet may be used than would otherwise be
necessary. Furthermore the sensitivity loss is at a
minimum if the front end is bent towards the screen over
such a distance as to engage the flared part of the
display tube.
When using the shape of the front end
as a design parameter, it has proved particularly
efficacious to shape the profile of the front end along
a path which encloses a polygon. In particular if this
path according to a preferred form of the deflection
unit according to the invention encloses a trapezium,
the frame defects as mentioned above prove to be
correctable effectively. (In this case the longer of the
two parallel sides of the trapezium should be deemed to
be nearest to the tube axis).
DESCRIPTION OF THE DRAWING
The
above and other features of the invention will now
be described in greater detail, by way of example,
with reference to the accompanying drawings, in
which:
FIG. 1 is a diagrammatic longitudinal sectional view of a display tube having a deflection unit.
FIG. 2 shows part of a line deflection coil of a known type for use in the deflection unit shown in
FIG. 3 shows diagrammatically the location of the front end of the coil shown in FIG. 2 when mounted on a display tube.
FIG. 4 shows a part of a line deflection coil for use in a deflection unit according to the invention.
FIG. 5 shows diagrammatically the location of the front end of the coil shown in FIG. 4 when mounted on a display tube.
FIG. 6 shows in principle the errors to be corrected by the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTFIG.
1 is a longitudinal sectional view through a color
television display tube 1 having a longitudinal tube
axis Z, a display screen 2 and three electron guns 4
situated in one plane. An electromagnetic deflection
unit 5 is mounted on the tube neck 3. The deflection
unit 5 comprises a pair of saddle coils 8 which form
the coil portions of the field deflection coil for the
field deflection, a pair of saddle coils 7 which form
the coil portions of the line deflection coil for the
line deflection, and a magnet core 6 surrounding the
coils in the form of a ring. The saddle coils 7 and 8
shown are of the so-called sherl type, which means that
their end sections adjacent the electron guns are not
situated in a plane perpendicular to the tube axis 6, as
are the end sections on the screen side, but are
situated in a plane parallel to the tube axis Z.
However, the invention is not restricted to the use of
this type of saddle coil.
FIG. 2 shows a saddle
shaped coil 9 of a conventional type having an arcuate
shaped front end section 10, an arcuate shaped rear end
section 11 and substantially axially extending
intermediate sections 12 and 13 which sections together
define a window 14. The profile of the front end
section 10 follows a path 15 which is accurately
adapted to the contour of the outer surface of the
display tube 1 for which the coil 9 is destined. FIG. 3
which is a diagrammatic sectional view of the coil 9 at
the area of the front end section 10 illustrates this.
Up till now, pairs of such coils 9 have been used as
the line deflection coil in conventional deflection
units.FIG.
4 shows a saddle shaped coil 16 which is used in a
line deflection coil in a deflection unit according
to the invention. The coil 16 consists of a front
end section 17, a rear end section 18 and
substantially axially extending conductors 19 and 20 which
sections and conductors define a window 21. In this
case the profile of the front end section 17 is formed
along a path 22 which is longer than a path which is
adapted to the contour of the outer surface of the
display tube 1 for which the coil 16 is destined. All
this is illustrated in FIG. 5 which is a diagrammatic
sectional view of the coil 16 at the area of the front
end section 17 and in which the contour of the outer
surface of the display tube is denoted by 23. The path 22
in this case encloses a trapezium shaped space the
longest parallel side of which faces the tube axis Z,
but in general the space to be enclosed may be in the
form of a polygon. In this case the rear end section
18 is shown to be horizontal, that is to say it does
not lie in a plane which is at an angle to the tube axis
as does the front end section 17. This coil shape is
sometimes referred to as "shell" coil, but the
invention is not restricted to this shape of coil.
The
favorable effect of the use of this shape of the
front end section 17 to correct raster defects may be
considered as follows. It is known that raster defects
are sensitive to variations of coil parameters on
notably the screen side of the deflection unit, while
the sensitivity to changes of parameters in the center
of the deflection unit and on the gun side is
directly reduced. However astigmatism is sensitive in
particular to coil parameters in the center and on the
screen side of the deflection unit and coma is
influenced in particular by coil parameters on the gun
side.
In coils of a "conventional" shape of the
front end section where the enclosed path length is a
minimum, the raster defects are produced
as follows. Primarily the deflection coil is
designed so that certain minimum requirements as
regards astigmatism and possibly also coma are
satisfied (in as far as this latter error is not
corrected for by means of provisions in the display
tube). This means that the coil parameters in the center
of the deflection coils are controlled optimally with
respect to the astigmatism. With respect to the
raster defects no further parameter variations are
possible and these errors are then to be taken as they
present themselves following the astigmatism control.
In
coils in which the shape of the front end section
may be freely chosen, extra design parameters are
available by which the astigmatism and also the raster
defects can be influenced.
It has been found
that several combinations of the coil parameters in the
center of the deflection coils and of the front end
section shape are possible which result in an
acceptable level of astigmatism while the raster defects
are always different. In this manner it is possible
to find a front end shape - coil parameter combination
with which the ultimate raster defects, for example, the
"undulation effect" has fully disappeared or has
been greatly reduced or that the pin-cushion
distortion in the East-West direction has been reduced
by a few percent, while it is even possible to deal
with both types of errors simultaneously.FIG.
6 shows diagrammatically, with reference to a
display screen 24, the raster defects on the upper
and lower sides of the display screen to be corrected
by a deflection unit according to the invention having
line deflection coils of the type shown in FIG. 4.
The raster lines 25 shown have an undulating variation
which is a frequently occurring shortcoming of
in-line display systems. By using line coils of the type
shown in FIG. 4 it was found that the raster lines
were influenced so that they formed a straight line in
the desired manner.

PHILIPS
30AX Cathode ray tube deflection unit comprising means
for compensating for misalignment of the line and
field deflection coil systems:A cathode
ray tube deflection unit comprising a field coil system
with two diametrically opposite field deflection
coils and a line coil system with two diametrically
opposite line deflection coils. Each coil has a front
end segment (15, 18), a rear-end segment (16, 19) and
conductors (17, 20) extending between such segments. In
order to prevent rotation of the horizontal lines of
the raster on the CRT display screen with respect to
the horizontal axis, which rotation is caused by
tolerance errors in alignment of the two coil systems, a
pair of plate-shaped parts (21, 21') of soft magnetic
material are arranged respectively extending across
the front end segment (15, 15') of the respective line
deflection coils (11, 11') in positions coinciding
with diametrically opposite vertices of a rectangle
whose diagnonals intersect substantially on the
longitudinal axis of the deflection unit, and at which
positions a portion of the front end segment of a line
deflection coil overlaps a portion of the front end
segment of a field deflection coil.

1. An
improved deflection unit for a cathode ray tube having a
longitudinal axis, a neck portion at one end of such
axis and a display
screen at the other end thereof, and a flared portion
connecting the neck portion with the display screen;
such deflection unit being adapted to be arranged
around said flared portion concentrically with said
longitudinal axis and comprising a field coil system
and a line coil system for deflecting an electron beam in
said tube in mutually orthogonal directions; the field
coil system comprising a pair of diametrically
opposite saddle-type field deflection coils located on
either side of a vertical axis of said deflection unit
and the line deflection coil system comprising a
pair of diametrically opposite saddle-type line
deflection coils located on either side of a horizontal
axis of said deflection unit; each of said coils having
a front end segment, a rear end segment and
conductors extending between such segments; such improvement
being characterized in that: said deflection unit
comprises a pair of plate-shaped parts of soft magnetic
material respectively extending across the front end
segment of respective ones of said pair of line
deflection coils in positions coinciding with
diametrically opposite vertices of a rectangle whose
diagonals intersect substantially on the longitudinal
axis of the deflection unit, and at each of which
positions a portion of a front end segment of a line
deflection coil overlaps a portion of a front end segment
of a field deflection coil. 2. A deflection unit as
claimed in claim 1, characterized in that the
plate-shaped parts have a width of approximately 3 mm, a
length which is substantially equal to the width of
the front end segment of the line deflection coil, and a
thickness of less than 0.5 mm.

Description:

BACKGROUND OF THE INVENTION
1. Field of the InventionThe
invention relates to a deflection unit for a
cathode ray tube having a neck portion and a display
screen, the deflection unit being arranged between
the neck portion and the display screen and around the
flared portion of the tube connecting the neck portion
and the display screen, the deflection unit comprising a
field coil system and a line coil system for
deflecting an electron beam produced in the neck
portion in mutually orthogonal directions; the field coil
system having a pair of diametrically opposite saddle
type field deflection coils located on either side
of a vertical axis and the line coil system having a pair
of diametrically opposite saddle type line
deflection coils located on either side of a horizontal
axis extending at right angles to the vertical axis;
each coil having a front end segment, a rear end segment
and conductors extending between the front and the
rear end segments.
2. Description of the Related Art
A
deflection unit of the above described type is known
from U.S. Pat. No. 4,229,720, issued Oct. 21, 1980,
which corresponds to Netherlands patent specification
No. 170,573 corresponding to U.S. Pat. No.
4,229,720, issued Oct. 21, 1988 and from the magazine
"Funkschau" No. 23, 1980, pages 88-92 published in West
Germany by Fanzis-Verlag GmbH published in West Germany.
In
a deflection unit of this type the line deflection
coils which generate a vertical magnetic field for the
horizontal deflection must be arranged at right angles
to the field deflection coils which generate a
horizontal magnetic field for the vertical deflection.
In the case of mutually orthogonal positions the
magnetic coupling between the coil pairs is equal to zero so
that no voltage is induced in the field deflection
coils as a result of the magnetic field generated by
the line deflection coils.
However, in practice
it may occur that due to mechanical inaccuracies and/or
manufacturing tolerances of the components during assembly
the line deflection coils are not arranged exactly at
right angles to the field deflection coils. In such a
case a voltage will be induced in the field
deflection coil as a result of the magnetic field of the
line deflection coils. Detrimental consequences
thereof are:
(a) the induced voltage reaches the
field deflection circuit and the high voltage thus
generated will disturb the operation of this field
deflection circuit,
(b) the induced voltage produces a
current through the field deflection coil via the
field deflection circuit so that a rotation of the
horizontal lines of the raster with respect to the
horizontal axis becomes visible on the display screen. The
convergence is also affected (twist errors).
SUMMARY OF THE INVENTIONIt
is an object of the invention to provide a means
which provides correction in a simple manner for the
possibility that in a deflection unit the line
deflection coils and the field deflection coils may not be
arranged exactly at right angles.
According to
the invention this is achieved by providing two
plate-shaped parts of a soft magnetic material near
the front end segments of the two line deflection coils
in positions which coincide with two diametrically
opposite vertices of a rectangle whose diagonals
intersect each other at least substantially on the
longitudinal axis of the deflection unit and at which
positions a portion of the front end segment of a line
deflection coil overlaps a portion of the front end
segment of a field deflection coil.
By
providing the soft-magnetic plate-shaped parts in the above
described manner the field lines are locally bundled
in such a manner that the flux through the field
deflection coils, and hence the coupling between the
field deflection coils and the line deflection coils,
is influenced so that the drawback mentioned above
under (a) is eliminated and the drawback mentioned under
(b) is greatly reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to the accompanying Figures wherein:
FIG. 1 is a diagrammatic cross-section (taken on the y-z plane) of a cathode ray tube with a deflection unit mounted thereon;
FIG.
2 is a diagrammatic perspective view of the field
deflection coils and line deflection coils, shown at a
distance from each other, of the deflection unit of
the cathode ray tube-deflection unit combination
shown in FIG. 1;
FIG. 3 is a front elevation on a
larger scale of a deflection unit consisting of the field
deflection coils and line deflection coils,
FIG.
4 is a diagrammatic cross-sectional view of the
conductors taken on the line IV--IV in FIG. 3 showing the
arrangement of a plate-shaped part with respect to
the conductors and;
FIG. 5 is an elevational view
of the display screen of the cathode ray tube of
FIG. 1, showing a rotation to be corrected by means of the
invention of the horizontal lines of the raster relative
to the horizontal axis X.
DESCRIPTION OF THE PREFERRED EMBODIMENTSFIG.
1 is a cross-sectional view of a display device
comprising a cathode ray tube 1 having an envelope 6
extending from a narrow neck portion 2 in which an
electron gun system 3 is mounted to a wide cone-shaped
portion 4 which is provided with a display screen. A
deflection unit 7 is mounted on the tube at the transition
between the narrow and the wide portion. This
deflection unit 7 has a support 8 of insulating material
with a front end 9 and a rear end 10. Between these
ends 9 and 10 there are provided on the inside of the
support 8 a system of deflection coils 11, 11' for
generating a line deflection magnetic field for
deflecting electron beams produced by the electron gun
system 3 in the horizontal direction, and on the
outside of the support 8 a system of deflection coils 12,
12' for generating a field deflection magnetic field
for deflecting electron beams procuced by the electron
gun system 3 in the vertical direction. The systems
of deflection coils 11, 11' and 12, 12' are surrounded
by an annular core 14 of a magnetisable material. The
separate coils 12, 12' of the system of field
deflection coils, as well as the coils 11, 11' of the system
of line deflection coils are of the saddle-type with
rear end segments positioned flat against the tube
wall. Deflection coils of the saddle type are
self-supporting coils comprising a number of conductors
which
are wound to form longitudinal first and second
side packets, an arcuate front end segment and an
arcuate rear end segment together defining a window
aperture. In such deflection coils the rear end
segments may be flared with respect to the profile of
the display tube (the original type of saddle coil) or
they may be arranged flat against the tube wall (in
this type of saddle coil the rear end segments
follows, as it were, the tube profile).As
has been shown in greater detail in FIGS. 2 and 3,
the deflection unit 7 has two line deflection coils
11 and 11' which are diametrically opposite to each
other and are arranged on either side of a horizontal
axis H, and two field deflection coils 12 and 12'
which are located diametrically opposite to each other
and are arranged on either side of a vertical axis V
extending at right angles to the horizontal axis H.
Each
line deflection coil consists of a front end
segment 15, a rear end segment 16 and conductors 17
connecting the front end segment 15 and the rear end
segment 16. Similarly, a field deflection coil 12 consists
of a front end segment 18, a rear end segment 19 and
conductors 20 connecting the front end segment 18 and
the rear end segment 19.
As explained and shown
in the Netherlands patent specification No. 170,573
mentioned in the preamble, the coils constituting the
deflection device are arranged in conventional manner
around a trumpet-shaped portion of a colour
television display tube, which trumpet-shaped portion
connects a display screen of the television display
tube to a neck portion of the relevant television display
tube. The arrangement is such that the longitudinal
axis of the deflection unit which is constituted by
the coils coincides with the longitudinal axis of the
display tube, whilst the front end segments 15 and 18 of
the line and field deflection coils are located at
the end of the deflection unit facing the display screen.

In
the following elaboration the quadrant in FIG. 3
located above the horizontal axis H and to the right of
the vertical axis V will be denoted the frist
quadrant, the quadrant located below the horizontal
axis H and to the right of the vertical axis V will be
denoted the second quadrant, the quadrant located below
the horizontal axis H and to the left of the vertical
axis V will be denoted the third quadrant and the
quadrant located above the horizontal axis H and to the
left of the vertical axis V will be denoted the fourth
quadrant.
Assuming that the current flows
through the line deflection coils as is indicated by the
arrows I and the line and field deflection coils are
arranged exactly at right angles to each other, line
deflection flux will enter the first quadrant in the
field deflection coil, which flux is equal to the line
deflection flux leaving the field deflection coil in
the second quadrant, so that the net line deflection flux
in the field deflection coil is equal to zero in this
case. The same applies to the line deflection coil
located in the third and fourth quadrants.
If,
however the symmetry plane of the two line deflection
coils 11, 11' has been slightly rotated clockwise with
respect to the horizontal axis H (for example, as a
result of manufacturing tolerances or the like) the
line flux entering the field deflection coil 12 in the
first quadrant will slightly decrease and the flux
leaving the second quadrant will slightly increase, so
that there is a net line deflection flux leaving the
field deflection coil 12. Correspondingly, a net line
deflection flux is obtained entering the field
deflection coil 12' located in the third and fourth
quadrants.The
(unwanted) result is that the horizontal lines of
the raster present a rotation with respect to the
horizontal (x) axis on the display screen 5 as shown in
FIG. 5.
In order to counteract this effect,
plate-shaped parts 21, 21' manufactured from a soft
magnetic material are provided near the transition of the
front end segments 15 into the conductors 17, on
diagonal D which extends through the longitudinal axis
of the deflection unit and across those ends of the front
end segments 15 of the line deflection coils 11, 11'
which are located furthest away from the horizontal
axis H as a result of the rotation in the direction of
the arrows C. Such plate-shaped parts, as shown in
FIG. 4, may have a L-shaped structure and whose long
limbs extend along the a portion of the front end
segments 15 of the line deflection coils which overlaps a
portion of the front end segments 18 of the field
deflection coils. The length of these limbs corresponds
with the width of the front end segment 15 at this
region. The short limbs of the L-shaped plate-shaped
parts extends over the edge of the relevant front end
segments of the line deflection coils towards the front
end segment 18 of the field deflection coil.
By
providing these plate-shaped parts or field conductors
manufactured from a soft magnetic material, the line
deflection flux entering the field deflection coil is
intensified in the first quadrant and the line
deflection flux leaving the field deflection coil in the
third quadrant is intensified, so that the above
described effect caused by the rotation of the line
deflection coils in the direction of the arrows C is
counteracted.
It will be evident from the foregoing
that in the case of a rotation of the symmetry plane of
the line deflection coils in an anti-clockwise
direction relative to the horizontal axis the
plate-shaped parts have to be provided on the line deflection coils at two diametrically opposite points located on the diagonal D'.
A
rotation of the line deflection coils with respect
to their desired position is mentioned above as an
example. However, the field deflection coils may deviate
from their symmetrical location, or both the line
deflection coils and the field deflection coils may have a
deviating location. In all these cases the present
invention provides a correction by arranging two
plate-shaped soft magnetic parts near the front end segments
of the two line deflection coils in positions which
coincide with two diametrically opposite vertices of a
rectangle whose diagonals intersect each other at
least substantially on the longitudinal axis of the
deflection unit and in which positions a portion of a
front end segment of a line deflection coil overlaps a
portion of the front end segments of a field deflection
coil. And in all these cases the explanation given for
their operation remains valid.
In one embodiment
parts 21, 21' were manufactured from an Si Fe alloy
having a thickness of 0.35 mm and a width of 3 mm,
which in a deflection unit as described in the article
mentioned in the preamble resulted in a coupling
influence of 9 mV at a voltage of 1 V across the line
deflection coils.
The influence of spreading, if not
corrected, is, for example, 6 mV in the case of an
incorrect arrangement, which results in a total range of
between -18 mV and +18 mV.
In this case this will be reduced to ±9 mV by using the correction means according to the invention.
In
practice the position of the correction means (the
plates 21, 21'), and hence the choice of the correct
diagonal, can be determined by measuring the phase
of the voltage produced across the field deflection
coil with respect to the voltage applied across the line
deflection coil.

Cathode-ray tube for displaying coloured pictures PHILIPS IN-LINE ELECTRON GUN SYSTEM TECHNOLOGY 30AX SYSTEM :By
deflecting the electron beams before the focusing
lenses in an electron gun system for a color display
tube towards the tube axis by non-symmetrical lens
fields so that they converge on the display screen,
it has proved possible to obtain symmetrical focusing lens
fields by means of mechanically non-symmetrical
electrodes the axes of which are parallel, if the beams
enclose a given angle with the gun axes. This enables
an easy manufacture of the electrodes and an accurate
assembly of the guns. In these guns the focusing of the
beams is independent of the convergence.

1.
An electric discharge tube comprising an envelope
having a main axis, a display screen and an electron
gun system for producing a plurality of electron
beams and converging the beams on the display screen,
the electron gun system comprising first electrode
means for generating the electron beams, the first
electrode means being situated along axes parallel to
the main axis of said tube; second electrode means
situated along the path of the electron beams between the
first electrode means and the display screen, said
second electrode means comprising respective last
electrodes situated on the side toward the dislay
screen and an associated preceding electrode, with
electrodes in use constitute a lens field which focuses
the electron beams symmetrically; and third
electrode means between the first and the second
electrode means for forming an asymmetric lens field to
coverge the electron beams on the display screen, characterized in that
the axes of the electrodes of all electrode means are parallel to said axes of the first electrode means; and
the
last electrodes (76, 96, 106), situated on the side toward
the display screen, of those second electrode means
which are situated eccentrically with respect to
the main axis of the tube, have axes (54) which are
situated eccentrically with respect to the axes (55) of
the associated preceding electrodes (75, 95, 105) and to
the axes (62) of the associated first electrode
means, the axes (55) of said preceding electrodes
(75, 95, 105) having a smaller distance to the main
axis of the tube than the axes (54) of the associated
last electrodes (76, 96, 106) situated on the side
toward the display screen, said axes (54) of said last
electrodes in turn having a smaller distance to the main
axis of the tube than the axes (62) of the associated
first electrode means (71, 72, 73, 91, 92, 93).
2.
An electric discharge tube as claimed in claim 1,
characterized in that all said axes are situated in one
plane, the axes of one of the first electrode means and
the associated second electrode means coincide with
the main axis of the tube, and the axes of two other
first and second electrode means are situated
symmetrically with respect to the main axis of the tube.

Description:

BACKGROUND OF THE INVENTION
The
invention relates to a colour display tube
comprising first electrode means to generate
plurality of electron beams, situated along axes
parallel to the main axis of said tube; a display screen
on which said electron beams converge; second electrode
means situated along the path of the electron beams
between the first electrode means and the display
screen, which second electrode means form a lens field
which focuses the electron beams symmetrically; and
third electrode means between the first and the second
electrode means with which, if desired in cooperation with
the first electrode means, an asymmetric lens field
is formed to converge the electron beams on the display
screen.
Such a colour display tube is
disclosed in U.S. Pat. No. 2,957,106. Such display tubes
are used inter alia as tubes to display coloured
pictures, as oscilloscope tubes, etc. In such tubes it
is desired for the electron beams to be converged in
one point on the display screen. In U.S. Pat. No.
2,957,106 an asymmetric electron lens is provided in the
path of the electron beams which do not coincide with
the main axis of the tube between the triode part of
the electron gun formed by the cathode, the first and
second grids, and the focusing lens, so that the
beams are deflected towards each other and converge
on the display screen. The focusing lens is formed by
a lens field between two electrodes. These
electrodes consist of curved electrode plates having
apertures therein. The plates are curved so as to be
always perpendicular to the electron path. By applying a
potential difference between the plates an electron
lens is formed which is symmetrical for the electron
beams and which has a focusing effect and focuses each
electron beam on the display screen. It is very
difficult to manufacture such very accurately curved
electrode plates and assemble them with respect to each
other. Electrodes of such electron guns are assembled
by means of assembly pins which have to enclose a very
accurate angle with respect to each other. In order
to be able to remove the guns from the assembly pins it
is necessary for these pins to be connected
detachably in a jig as a result of which their mutual
angle becomes less accurate as a result of detrition,
diurt, bending an breaking of the pins.
This
problem is recognized in U.S. Pat. No. 3,906,279 and a
solution to this problem is given. This patent teaches a
construction for the convergence of three electron
beams from three assembled electron guns whch operate
independently of each other and the axes of which are
parallel and hence parallel assembly pins can be used.
This construction is characterized in that of each
electron gun which is situated eccentrically with
respect to the main axis of the tube, the last
electrode situated on the side of the display screen has an
axis which is situated eccentrically with respect to
the axis of the relevant electron gun in a plane
through the main axis of the tube and the axis of the
electron gun and at a larger distance from the main
axis of the tube than the axis of the electron gun. This
last electrode also has a larger diameter than the other
electrodes of the electron gun. As a result of the
eccentrically placed last electrodes, convergence of
the electron beams is obtained in a simple manner and
at the same time the electron beams are each focused
separately.
U.S. Pat. No. 3,772,554 discloses an integrated system
of electron guns operating in an analogous manner. A
system of electron guns operating in an analogous
manner and in which the focusing lenses of the guns not
situated on the tube axis are asymmetrical is known
from German Patent Application 2,406,443 laid open to
public inspection. All these constructions are less
attractive because they exhibit a very important
disadvantage. A variation of the strength of the focusing
lens in such guns at the same time has a direct
influence on the convergence of the electron beams,
which is not desired.
SUMMARY OF THE INVENTION
It
is therefore the object of the invention to provide a
simple construction for focusing and converging
electron beams independently of each other by means
of electron guns the axes of which are parallel so
that a simple, rapid and accurate manufacture and
assembly are possible.
According to the invention, a
colour display tube of the kind mentioned in the
opening paragraph is characterized in that the axes of
the electrodes of all electrode means are parallel to the
axes axes and that of the second electrode means
which are eccentric with respect to the main axis of
the tube, the last electrodes (76, 96, 106) situated on
the side of the display screen have axes (54) which
are eccentric with respect to the axes (55) of the
associated preceding electrodes (75,95, 105) and to the
axes (62) of the associated first electrode means, the
axes (55) of those preceding electrodes (75, 95, 105)
having a smaller distance to the main axis of the
tube than the axes (54) of the associated last
electrodes (76, 96, 106) situated on the side of the
display screen, the last-electrode axes (54) in turn
having a smaller distance to the main axis of the tube than
the axes (62) of the associated first electrode means
(71, 72, 73, 91, 92, 93).
The invention is
based on the recognition that, when an electron beam is
incident in such a mechanically non-symmetric electrode
system at a given angle with the gun axis, a
symmetric focusing of the electron beam can nevertheless
be obtained so that a variation of the strength of the
focusing lens has no influence on
the convergence. This given angle which depends on
the gun dimensions can be determined experimentally on
an optical bench.
A preferred embodiment of such a
colour display tube embodying the invention is
characterized in that all these axes are situated in
one plane and the axes of one of the first electrode
means and the associated second electrode means coincide
with the main axis of the tube and the axis of two other
first and second electrode means are situated
symmetrically with respect to the main axis of the tube.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to a drawing, in which:
FIG. 1 is a cross-sectional view of a colour display tube embodying the invention,
FIGS. 2 and 3 are cross-sectional views of prior-art electron guns, and
FIGS.
4 to 6 are cross-sectional views of a number of
embodiments of electron guns used in colour display
tubes embodying the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG.
1 is a cross-sectional view of a colour display
tube embodying the invention. In a neck 4 of a glass
envelope 1 further composed of a display window 2
and a conical part 3, three electron guns 5, 6 and
7 are provided which generate the electron beams 8,
9 and 10. The axes of these electron guns are
situated in one plane, the plane of the drawing. The
axis of the central electron gun 6 coincides with the
main axis 11 of the envelope. The three electron guns
consist of a number of cylindrical electrodes placed
along an axis. As is known, it is possible to construct
one or more of the juxtaposed electrodes of the guns
as one assembly. A large number of triplets of phosphor
lines are provided on the inside of the display
window. Each triplet comprises a line consisting of a
green luminescing phosphor, a line consisting of a blue
luminescing phosphor and a line consisting of a red
luminescing phosphor. All triplets together constitute
the display screen 12. The phosphor lines extend
perpendicularly to the plane of the drawing. A shadow mask
13 having a large number of elongate apertures 14
parallel to the phosphor lines, through which apertures
the electron beams 8, 9 and 10 pass, is placed before
the display screen. Since the electron beams
enclose a small angle with each other and converge on the
display screen, each beam is incident only on phosphor
lines of one colour via the elongate apertures. As is
known, it is alternatively possible to provide the
electron guns in a triangular arrangement in the tube,
each gun being situated at the corner of an
equilateral triangle. In that case the shadow mask has
circular apertures and the display screen is composed
of triplets of phosphor dots.
FIG. 2 is a
cross-sectional view of a prior-art electron gun (U.S. Pat.
No. 3,957,106). The means to generate the electron
beams each consist of a cathode 15, a grid electrode 16
and an accelerating electrode 17. The convex portion
19 of electrode 18 is provided with apertures 20 and
21. As a result of the convex portion 19 of
electrode 18 a non-symmetrical electrostatic field is formed
between the electrodes 17 and 18 so that the
electrode beams 22 and 23 are bent towards the axis 24
in such manner that these beams converge on the
display screen 12. The apertures 25 and 26 in electrode 27
and the apertures 28 and 29 in electrode 30 are
provided so that they are placed in the path of the
electron beams. The curvature of the convex portions of
the electrodes 27 and 30 in which said apertures are
provided is such that their surfaces always extend
perpendicularly to the paths of the electron beams. As a
result of this and by applying a sufficiently large
potential difference between the electrodes 27 and 30 a
symmetrical lens field is obtained between the
electrodes which has a symmetric focusing effect on the
electron beams. As a rsult of this, variations in strength
of the lens field have no influence on the
convergence. The manufacture of electrodes having such
accurately curved surfaces is very difficult and the
assembly is inaccurate because assembly pins have to be
used which enclose an angle
with each other. FIG. 3 shows a system of electron
guns (U.S. Pat. No. 3,906,279) in which all the axes 31,
32 and 33 of the electron guns 34, 35 and 36 extend
parallel to each other and are situated in one
plane. The gun 34 has a cathode 37 and a grid 38 and an
anode 39 and grids 40 and 41. The corresponding
electrodes of gun 35 are referenced 47 to 51. The
corresponding electrodes of gun 36 are referenced 57 to
61.
As is shown in this Figure, the grids 41
and 61 have a larger diameter than the associated
grids 40 and 60 and the axes 42 and 43 are situated
farther away from the axes 32 than the gun axes 31 and 33.
The lens fields between the electrodes 40 and 41 and
between the electrodes 60 and 61 are hence not
symmetrical and deflect the beams 44 and 45 towards
the central beam 46. These lens fields and the lens
field between the grids 50 and 51 also serve to focus the
electron beams. A small variation in the voltage
difference between the electrodes 40 and 41 and
between the electrodes 60 and 61 hence has an influence
on the convergence and also on the focusing of the
electron beams. It will be obvious that this is
undesired since it should be possible to provide
variations in the focusing and convergence preferably
independently of each other.
FIG. 4 shows a first
embodiment of an electron gun system in which no curved
parts are necessary, all the axes of the electrodes
extend parallel to each other and nevertheless a
convergence is possible
which is independent of the focusing voltage (the
voltage difference between the last two electrodes in
an electron path). It consists of three guns 70, 80
and 90 having the cathodes 71, 81 and 91 in grids 72,
82 and 92 and opposite to the electrodes 73, 83 and
93. By means of these electrode means, three electron
beams 74, 84 and 94 are generated which initially
extend parallel to each other. By providing the grids
75 and 95 with apertures 52 and 53 which are situated so
as to be not symmetrical with respect to the beams 74
and 94, the electron beams 74 and 94 are deflected
towards the central electron beam 84 in a manner
analogous to that of U.S. Pat. No. 2,957,106. The
focusing is done by the lens fields between the
electrodes 75 and 76, 85 and 86 and 95 and 96. In
contrast with the construction disclosed in U.S. Pat. No.
3,906,279, any variation of the focusing lens fields
between the electrodes 75 and 76 and between the
electrodes 95 and 96 of the outermost electron guns has
no influence at all on the convergence because the
electron beams 74 and 94 are incident through said lens
fields at a given angle with the gun axes. As a result
of this, a focusing lens acting symmetrically on the
beam is obtained by means of a few electrodes which are
situated non-symmetrically.
An example of the
electric voltages (in Volts) applied to the various
electrodes is shown in FIG. 4 for gun 70. A number of
dimensions of electrodes and their mutual distances are
recorded in the table below:

The distance from axis 54 of
electrode 76 to the gun axis 62 is 0.3 mm. The
distance from axis 55 to axis 62 is 0.4 mm and the distance
from axis 56 to axis 62 is 0.2 mm. For other gun
dimensions, other mutual axial distances are necessary.
These can be determined experimentally on an optical
bench or can be calculated. The thickness of the
material (Cr-Ni-steel) from which the varous electrodes
are manufactured is in this embodiment 0.13 to 0.2 mm.
The distance between two gun axes is 10 mm. FIG. 5
is a cross-sectional view of a second embodiment of an
electron gun system according to the invention.
For
clarity, the same reference numerals are used as in
FIG. 4. The convergence of the electron beams 74, 84
and 94 is obtained in this embodiment by causing the
ends of the electrodes 75 and 95 situated oppositely to
the electrodes 73 and 93 to enclose an angle of
approximately 87° with the gun axis. This convergence
method is also disclosed already in U.S. Pat. No.
2,957,106. The various dimensions correspond
approximately to the dimensions indicated with reference
to FIG. 4. The electron beams 74, 84 and 94 also
converge on the display screen 12. The convergence is
independent of the strength of the focusing lens. The
convergence of the electron beams can alternatively be
obtained by shifting and/or tilting the electrodes 73
and 93 as a result of which the non-symmetrical
deflecting lenses are obtained in cooperation with the
electrodes 75 and 95. This will not be further
described.
FIG. 6 is a cross-sectional
view of a third embodiment of an electron gun
system embodying the invention. The electron gun
system comprises a number of electrodes 102, 103,
105 and 106 which are constructed so as to be common for
the three electron beams. The Figure is drawn
approximately to the same scale as FIGS. 4 and 5. For
clarity, the same reference numerals are used as much
as possible as in FIGS. 4 and 5. It will be obvious that
one of the electrodes may be divided into two
sub-electrodes or that an extra electrode may be added
without this influencing the essence of the invention.

CRT TUBE PHILIPS 30AX TECHNOLOGY
Method of Production / manufacturing a color
display CRT tube and color display tube manufactured
according to said method.A ring is
provided to correct the convergence, color purity and
frame errors of a color display tube which ring is
magnetized as a multipole and which is secured in or
around the tube neck and around the paths of the
electron beams.
The magnetization of such a ring can
best be carried out by energizing a magnetization unit
with a combination of direct currents thereby
generating a multipole magnetic field and then
effecting the magnetization by generating a decaying
alternating magnetic field which preferably varies its
direction continuously.

1.
A method of manufacturing a color display tube in
which magnetic poles are provided in or around the
neck of said tube and around the paths of the electron
beams, which poles generate a permanent static
multipole magnetic field for the correction of errors in
convergence, color purity and frame of the display
tube, which magnetic poles are formed by the magnetisation
of a configuration of magnetisable material provided
around the paths of the electron beams, the method
comprising energizing a magnetisation device with a
combination of direct currents with which a static
multipole magnetic field is generated, and superimposing a
decaying alternating magnetic field over said static
multipole magnetic field which initially drives said
magnetisable material into saturation on either side of
the hysteresis curve thereof, said decaying
alternating magnetic field being generated by a decaying
alternating current. 2. The method as claimed in claim 1,
6 or 7, wherein the decaying alternating magnetic
field is generated by means of a separate system of
coils in the magnetisation device. 3. The method as
claimed in claim 2, wherein the decaying alternating
magnetic field varies its direction continuously. 4. The
method as claimed in claim 3 wherein the frequency of
the decaying alternating current is approximately the
standard line frequency. 5. A colour display tube
manufactured by means of the method as claimed in claim
4. 6. The method as claimed in claim 1 which further
comprises erasing any residual magnetism in said
configuration, prior to said magnetisation, with an
alternating magnetic field. 7. The method as claimed in
claim 6 which further comprises correcting the errors in
convergence, color purity and frame of the display
picture with a combination of direct currents applied
to said magnetisation device and then reversing said
direct currents while increasing the magnitudes thereof
and applying these adjusted direct currents to said
magnetisation device for the magnetisation of said
configuration.

Description:

BACKGROUND OF THE INVENTION
The
invention relates to a method of manufacturing a
color display tube in which magnetic poles are
provided in or around the neck of the envelope and
around the paths of the electron beams, which poles
generate a permanent multipole magnetic field for the
correction of the occurring errors in convergence, color
purity and frame of the color display tube, which
magnetic poles are formed by the magnetisation of a
configuration
of magnetisable material provided around the paths of
the electron beams, which configuration is
magnetized by energising a magnetising device with a
combination of currents with which a static multipole
magnetic field is generated.
The invention also relates to a color display tube manufactured according to said method.
In
a color display tube of the "delta" type, three
electron guns are accommodated in the neck of the tube
in a triangular arrangement. The points of
intersection of the axes of the guns with a plane
perpendicular to the tube axis constitute the corner points
of an equilateral triangle.
In a color display
tube of the "in-line" type three electron guns are
arranged in the tube neck in such manner that the axes
of the three guns are situated mainly in one plane
while the axis of the central electron gun coincides
substantially with the axis of the display tube. The
two outermost electron guns are situated symmetrically
with respect to the central gun. As long as the
electron beams generated by the electron guns are not
deflected, the three electron beams, both in tubes of
the "delta" type and of the "in-line" type, must
coincide in the center of the display screen (static
convergence). Because, however, as a result of defects
in the manufacture of the display tube, for example,
the electron guns are not sealed quite symmetrically
with respect to the tube axis, deviations of the frame
shape, the color purity and the static convergence
occur. It should be possible to correct said
deviations.
Such a color display tube of the
"in-line" type in which this correction is possible,
is disclosed in Netherlands Pat. application No.
7,503,830 laid open to public inspection. Said
application describes a color display tube in which the
deviations are corrected by the magnetisation of a ring
of magnetisable material, as a result of which a
static magnetic multipole is formed around the paths of
the electron beams. Said ring is provided in or around
the tube neck. In the method described in said patent
application, the color display tube is actuated after
which data, regarding the value and the direction of
the convergence
errors of the electron guns, are established, with
reference to which the polarity and strength of the
magnetic multipole necessary to correct the frame,
color purity and convergence errors are determined. The
magnetisation of the configuration, which may consist
of a ring, a ribbon or a number of rods or blocks
grouped around the electron paths, may be carried out in
a number of manners. It is possible, for example,
first to magnetise the configuration to full
saturation, after which demagnetisation to the desired
value is carried out with an opposite field. A
disadvantage of this method is that, with a
combination of, for example, a 2, 4, and 6-pole field, the
polarity and strength of the demagnetisation vary
greatly and frequently, dependent on the place on the
ring, and hence also the polarity and strength of the
full magnetisation used in this method. Moreover it
appears that the required demagnetising field has no
linear relationship with the required correction field.
Due to this non-linearity it is not possible to use a
combined 2, 4 and 6-pole field for the
demagnetisation. It is impossible to successively carry
out the 2, 4 and 6-pole magnetisation since, for each
magnetisation, the ring has to be magnetised fully,
which results in the preceding magnetisation being erased
again. The possibility of successively magnetising
various places on the ring is very complicated and is not
readily possible if the ring is situated in the tube
neck since the stray field of the field necessary for
the magnetisation again demagnetizes, at least partly,
the already magnetised places.
SUMMARY OF THE INVENTIONIt
is therefore an object of the invention to provide a
method with which a combined multipole can be
obtained by one total magnetisation.
According to
the invention, a method, of the kind described in the
first paragraph with which this is possible, is
characterized in that the magnetisation is effected
by means of a decaying alternating magnetic field which
initially drives the magnetisable material on either side
of the hysteresis curve into saturation. After the
decay of the alternating magnetic field, a hard
magnetisation remains in the material of the
configuration which neutralizes the externally applied
magnetic field and is, hence, directed oppositely thereto.
After switching off the externally applied magnetic
field, a magnetic multipole field remains as a result
of the configuration magnetized as a multipole. The
desired magnetisation may be determined in a number of
manners. By observing and/or measuring the deviations
in the frame shape, color purity and convergence, the
desired multipole can be determined experimentally and
the correction may be carried out by magnetisation of
the configuration. If small deviations are then
still found, the method is repeated once or several times
with corrected currents. In this manner, by repeating
the method according to the invention, it is possible
to produce a complete correction of the errors in
frame, color purity and convergence. Preceding the
magnetisation, residual magnetism, if any, in the
configuration is preferably erased by means of a
magnetic field.
The method is preferably carried out by determining the required correction field prior to the magnetisation
and, after the erasing of the residual magnetism,
by correcting the errors in the convergence, the
color purity and the frame of the displayed picture by
means of a combination of currents through the
magnetising device, after which the magnetisation is
produced by reversing the direction of the
combination of currents, increasing the current strength
and simultaneously producing the said decaying
alternating magnetic field.
The correction field,
obtained with the magnetizing device and measured along
the axis of the electron beams, is generally longer
than the multipole correction field generated by the
configuration. So the correction of the deviations will
have to be carried out over a shorter distance along
the axis of the tube, which is possible only with a
stronger field. During the magnetisation, a combination
of currents, which in strength and direction is in the
proportion of m:1 to the combination of currents
which is necessary to generate a correction multipole
field with the device, where m is, for example, -3,
should flow through the magnetisation device. The value of
m depends on the ratio between the length of the
correction multipole field, generated by the magnetizing
device, to the effective field length of the
magnetized configuration. This depends upon a number of
factors, for example, the diameter of the neck, the kind
of material, the shape and the place of the
configuration, etc., and can be established
experimentally. If it proves, upon checking, that the
corrections with the magnetized configuration are too large
or too small, the magnetisation process can be repeated
with varied magnetisation currents.
The
decaying alternating magnetic field can be generated
by superimposing a decaying alternating current on the
combination of currents through the magnetisation device
(for example, a device as disclosed in Netherlands
Pat. application No. 7,503,830 laid open to public
inspection). The decaying alternating magnetic field is
preferably generated in the magnetisation device by means
of a separate system of coils. In order to obtain a
substantially equal influence of all parts of the
configuration by the decaying alternating field, it is
recommendable not only to cause the alternating field to
decay but also to cause it to vary its direction
continuously. The system of coils therefore consists
preferably of at least two coils and the decaying
alternating currents through the coils are shifted in
phase with respect to each other. Standard line frequency
(50 or 60 Hz) has proven to give good results. The
phase shift, when using coils or coil pairs, the axes
of which enclose angles of 120° with each other, can
simply be obtained from a three-phase line.
DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to a drawing, in which
FIG.
1 is a diagrammatic sectional view of a known color
display tube of the "in-line" type having an
external static convergence unit,
FIG. 2 shows the pinion transmission used therein,
FIGS.
3 and 4 are two diagrammatic perpendicular
cross-sectional views of the color display tube with a
ring, which has not yet been magnetized, and in which
the outermost electron beams do not converge
satisfactorily,
FIGS. 5 and 6 are two diagrammatic
perpendicular sectional views of a color display tube in
which convergence by means of the magnetisation device
has been obtained,
FIGS. 7 and 8 show the magnetisation of a ring arranged in the system of electron guns,
FIGS.
9 and 10 show two diagrammatic perpendicular
sectional views of a color display tube with a
magnetized ring with which the convergence error, as
shown in FIG. 4, is removed,
FIGS. 11 and 12 show two types of devices suitable for magnetisation according to the invention, and
FIGS. 13 to 18 show parts of another type of magnetisation unit.
DESCRIPTION OF THE PREFERRED EMBODIMENTSFIG.
1 is a diagrammatic sectional view of a known color
display tube of the "in-line" type. Three electron
guns 5, 6 and 7, generating the electron beams 8, 9
and 10, respectively, are accommodated in the neck 4
of a glass envelope 1 which is composed of a display
window 2, a funnel-shaped part 3 and a neck 4. The axes
of the electron guns 5, 6 and 7 are situated in one
plane, the plane of the drawing. The axis of the central
electron gun 6 coincides substantially with the tube
axis 11. The three electron guns are seated in a
sleeve 16 which is situated coaxially in the neck 4.
The display window 2 has on the inner surface thereof
a large number of triplets of phosphor lines. Each
triplet comprises a line of a phosphor luminescing green, a
line of a phosphor luminescing blue, and a line of a
phosphor luminescing red. All of the triplets
together constitute a display screen 12. The phosphor
lines are normal to the plane of the drawing. A shadow
mask 12, in which a very large number of elongate
apertures 14 are provided through which the electron
beams 8, 9 and 10 pass, is arranged in front of the
display screen 12. The electron beams 8, 9 and 10 are
deflected in the horizontal direction (in the plane of
the drawing) and in the vertical direction (at right
angles thereto) by a system 15 of deflection coils. The
three electron guns 5, 6 and 7 are assembled so that
the axes thereof enclose a small angle with respect to
each other. As a result of this, the generated electron
beams 8, 9 and 10 pass through each of the apertures
14 at said angle, the so-called color selection angle,
and each impinge only upon phosphor lines of one color.A
display tube has a good static convergence if the
three electron beams, when they are not being
deflected, intersect each other substantially in the
center of the display screen. It has been found,
however, that the static convergence often is not good,
no more than the frame shape and the color purity,
which may be the result of an insufficiently accurate
assembly of the guns, and/or sealing of the electron
guns, in the tube neck. In order to produce the static
convergence, so far, externally adjustable correction
units have been added to the tube. They consist of a
number of pairs of multipoles consisting of magnetic
rings, for example four two-poles (two horizontal and two
vertical), two four-poles and two six-poles. The
rings of each pair are coupled together by means of a
pinion transmission (see FIG. 2), with which the rings are
rotatable with respect to each other to an equal
extent. By rotating the rings with respect to each
other and/or together, the strength and/or direction of
the two-, four- or six-pole field is adjusted. It
will be obvious that the control of a display tube
with such a device is complicated and time-consuming.
Moreover, such a correction unit is material-consuming
since, for a combination of multipoles, at least
eight rings are necessary which have to be provided
around the neck so as to be rotatable with respect to each
other.
In the Netherlands Pat. application No.
7,503,830, laid open to public inspection, the
complicated correction unit has, therefore, been
replaced by one or more magnetized rings, which rings
are situated in or around the tube neck or in or
around the electron guns.
However, it has proved
difficult with the magnetising methods known so far to
provide a combination of multipoles in the ring by
magnetisation.
The method according to the invention provides a solution.
For clarity, identical components in the following figures will be referred to by the same reference numerals as in FIG. 1.FIG.
3 is a diagrammatic sectional view of a display
tube in which the electron beams do not converge in
the horizontal direction. As is known, the outermost
electron beams can be deflected more or less in the
opposite direction by means of a four-pole, for example,
towards the central beam or away therefrom. It is also
possible to move the beams upwards and downwards. By
means of a six-pole the beams can be deflected more
or less in the same direction. For simplicity, the
invention will be described with reference to a display
tube which requires only a four-pole correction. The
convergence errors in the horizontal direction of the
electron beams 8 and 10 are in this case equally large
but opposite.
FIG. 4 is a sectional view of FIG.
3. On the bottom of sleeve 16, a ring 18 is provided
of an alloy of Fe, Co, V and Cr (known as Vicalloy)
which can be readily magnetized. It will be obvious
that the ring may alternatively be provided in other
places around the guns or in or around the tube neck.
Instead of a ring it is alternatively possible to use a
ribbon or a configuration of rods or blocks of
magnetisable material.
In FIG. 5 a device 19 for
generating a controllable multipole magnetic field is
provided around the neck 4 and the ring 18 according to
the method of the invention. 2-, 4- or 6-poles and combinations
thereof can be generated by means of the device 19.
For the tube shown in FIG. 3, only a four-pole
correction is necessary. The coils of the device 19,
which device will be described in detail hereinafter,
are in this case energized as four-poles until the point
of intersection S of the three electron beams 8, 9
and 10, which in FIG. 3 was situated outside the tube
1, lies on the display screen 12. The current I
through the coils of the device originates from a
direct current source B which supplies a current -mI 1
(m being an experimentally determined constant
>1) to the coils via a current divider and
commutator A. The current can be adjusted per coil so as
to generate the desired multipole. In this phase of the
method, an alternating current source C does not yet
supply current (i=0).
FIG. 6 is a perpendicular sectional view of FIG. 5. The current I 1
is a measure of the strength of the required
correction field. The correction field of the multipole
of the device 19 extends over a larger length of
the electron paths than the magnetic field generated
later by the magnetized ring. Therefore the field of
the ring is to be m-times stronger.FIG.
7 shows the step of the method in which the ring 18
is magnetized as a four-pole. As follows from the
above, in this preferred embodiment of the method,
the current through the coils of the device must be -mI
1 during the magnetisation, so must
traverse in the reverse direction and be m-times as
large as the current through the coils during the
correction. Moreover, the alternating current source C
supplies a decaying alternating current (i=i 1
>0) to the device 19, with which current the
decaying alternating field is generated. When the
alternating current is switched on, it must be so large
that the ring 18 is fully magnetized on either side of
the hysteresis curve. When the alternating field has
decayed, the ring 18 is magnetized, in this case as a
four-pole. It is, of course, alternatively possible to
magnetise the ring 18 as a six-pole or as a two-pole or
to provide combinations of said multipoles in the
ring 18 and to correct therewith other convergence
errors or color purity and frame errors. It is also
possible to use said corrections in color display tubes of
the "delta" type.FIG.
9 shows the display tube 1 shown in FIG. 3, but in
this case provided with a ring 18 magnetized
according to the method of the invention as shown in
FIGS. 5 and 7. The convergence correction takes place
only by the magnetized ring 18 present in sleeve 16. The
provision of the required multipole takes place at
the display tube 1 factory and complicated adjustments
and adjustable convergence units (FIG. 2) may be
omitted.
FIG. 10 is a cross-sectional view
perpendicular to FIG. 9. FIG. 11 shows a magnetisation
device 19 comprising eight coils 20 with which the
convergence (see FIG. 5) and the magnetisation (see
FIG. 7) are carried out. For generating the decaying
alternating magnetic field, two pairs of coils 21 and
22, extending in this case at right angles to each
other, are incorporated in the device 19. The current i
a through the pair of coils 21 is shifted in phase through 90° with respect to the current i b
through the other pair of coils 22, so that the
decaying alternating magnetic field changes its
direction during the decay and is a field circulating
through the ring 18. FIG. 12 shows a magnetisation device
known from Netherlands Pat. application No.
7,503,830 laid open to public inspection. In this
case, the decaying alternating current may be
superimposed on the direct current through the coils 23
so that extra coils are not necessary in the device.
The coils 23 are wound around a yoke 24.
The
magnetisation device 19 may alternatively be composed of a
combination of electrical conductors and coils, as
is shown diagrammatically in FIGS. 13 to 18.
FIG.
13 is a sectional view of the neck 4 of a display
tube 1 at the area of a ring 18 to be magnetised. A
two-pole field for corrections in the horizontal
direction is generated in this case by causing currents
to flow through the conductors 25, 26, 27 and 28 in the
direction as shown in the figure. Said conductors may
be single wires or wire bundles forming part of one
or more coils or turns, and extending parallel to
the tube axis at the area of the ring 18.
FIG. 14
shows how, in an analogous manner, a four-pole field for
corrections of the outermost beams 8 and 10 in the
horizontal direction can be generated by electrical
conductors 29, 30, 31 and 32. A four-pole field for
corrections of the outermost beams 8 and 10 in the vertical
direction is substantially the same. However, the
system of conductors 29, 30, 31 and 32 is rotated
through 45° with respect to the neck 4 and the axis of
the tube 1.
FIG. 15 shows, in an analogous
manner, a six-pole for corrections in the horizontal
direction with conductors 33 to 38. By means of a
combination of conductors (wires or wire bundles) with
which 2-, 4- and 6-poles can be generated, all
combinations of two-, four- and six-pole fields with
the desired strength can be obtained by variations of the
currents through said conductors 33 to 38.
The
decaying alternating magnetic field in a magnetisation
unit with conductors as shown in FIGS. 13, 14 and 15
can be obtained by means of coils positioned
symmetrically around the neck 4 and the conductors as
shown in FIGS. 16 and 17 or 18. By energizing the coils 39
and 40, shown in FIG. 16, with a decaying
alternating current, a decaying alternating magnetic
field is generated. A better influencing of the ring
18 by the decaying alternating field is obtained when a
system of coils having coils 41 and 42 in FIG. 17 is
provided which is rotated 90° with respect to the coils
39. In this case, 40 and the decaying alternating
current through the coils 41 and 42 should then
preferably be shifted 90° in phase with respect to the
decaying alternating current through the coils 39 and 40.
It is alternatively possible to generate the decaying alternating
magnetic field with one or more systems of coils as
shown in FIG. 18. The coils 43, 44 and 45 are
situated symmetrically around the tube axis and are
energized with decaying alternating currents which are
shifted 120° in phase with respect to each other (for
example from a three-phase line).

CRT TUBE PHILIPS 30AX TECHNOLOGY
Method of manufacturing a static convergence unit,
and a color display tube comprising a convergence
unit manufactured according to the method, PHILIPS 30AX INTERNAL STATIC CONVERGENCE SYSTEM Application technology:IMACO RING (Integrated Magnetic Auto Converging )The
method according to the invention consists in the
determination of data of the convergence errors of a
color display tube, data being derived from the said
determinations for determining the polarity and the
intensity of magnetic poles of a structure. The structure
thus obtained generates a static, permanent,
multipole magnetic field adapted to the convergence
errors occurring, so that the errors are connected.

What
is claimed is: 1. A method of producing a magnetic
convergence structure for the static convergence of
electron beams which extend approximately in one plane
in a neck of a color display tube of the kind in which
the neck merges into a flared portion adjoined by a
display screen, said method comprising providing around
the neck of the color display tube an auxiliary
device for generating variable magnetic fields in the
neck of the color display tube, activating the color
display tube, adjusting the auxiliary device to produce
a magnetic field for converging the electron beams,
determining from data derived from the adjustment of
the auxiliary device the extent and the direction of
the convergence error of each electron beam, and using
such data to determine the polarity and the intensity
of magnetic poles of said magnetic convergence
structure for generating a permanent multi-pole static
magnetic field for the correction of the convergence
errors occuring in the color display tube. 2. A method
as claimed in claim 1, wherein the auxiliary device
comprises an electromagnet convergence unit which
comprises a number of coils, said generating step
comprising passing electrical currents through said
coils for generating a magnetic field required for the
static convergence of the electron beams, and said
determining step comprising using the values of the
electrical currents for determining the permanent magnetic
structure. 3. A method as claimed in claim 2, further
comprising storing the data from the auxiliary
device in a memory. 4. A method as claimed in claim 2,
wherein said using step comprises controlling a
magnetizing unit for magnetizing an annular
magnetizable convergence structure. 5. A method as claimed
in claim 2, further comprising converting the data into a
code, and constructing said annular permanent
magnetic convergence structure having a desired
magnetic field strength from a set of previously
magnetized structural parts. 6. A method as claimed in
claim 1, further comprising forming the convergence
structure from a magnetizable mass which is annularly
arranged on at least one wall of the neck of the
color display tube. 7. A method as claimed in claim 1,
further comprising forming the convergence structure from a
magnetizable ring which is arranged on the neck of
the color display tube. 8. A method as claimed in
claim 1, wherein the convergence structure comprises a
non-magnetizable support and a number of permanent
magnetic dipoles. 9. A method as claimed in claim 4,
wherein said magnetizing step cofmprises polarizing
the magnetizable material of the annular convergence
structure at one location after the other by means of
the magnetizing unit. 10. A method as claimed in claim 4,
further comprising assemblying the auxiliary device and
the magnetizing unit in one construction, and then
enclosing a convergence structure to be magnetized
with said magnetizing unit. 11. A method as claimed in
claim 10, further comprising displacing said
construction with respect to said tube after said
determining step.

Description:

The
invention relates to a method of manufacturing a
magnetic convergence device for the static convergence
of electron beams which extend approximately in one
plane in a neck of a colour display tube, and to a
colour display tube provided with a permanent magnetic
device for the static convergence of electron beams in
the colour display tube. A known device, described in
U.S. Pat. No. 3,725,831, consists of at least four
permanent magnetic rings arranged in pairs which generate a
magnetic field that can be adjusted as regards
position and intensity. The adjustability is obtained by
turning the two rings of a pair in the same direction
with respect to the electron beams and by turning the
one ring in the opposite direction with respct to the
other ring. The adjustability necessitates that the
rings be arranged on a support which is arranged about
the neck of the colour display tube and which should
include facilities such that the adjustability of each
pair of rings, independent of the position of the other
rings, is ensured. The invention has for its object
to provide a method whereby a device for converging
electron beams can be manufactured which need not be
mechanically adjustable, so that it can have a very
simple construction, and to provide a colour display
tube including such a device.To
this end, the method according to the invention is
characterized in that the colour display tube is
activated, after which data concerning the extent and
the direction of the convergence error of each electron
beam are determined, on the basis of which is
determined the polarity and intensity of magnetic
poles of a structure for generating a permanent,
multi-pole, static magnetic field for the correction of the
convergence errors occurring in the colour display
tube, about the neck of the colour display tube there
being provided an auxiliary device for generating
variable magnetic fields in the neck of the colour
display tube, the auxiliary device being subsequently
adjusted such that a magnetic field with converges the
electron beams is produced, data being derived from the
adjustment of the auxiliary device thus obtained, the
said data being a measure for the convergence errors and
being used for determining the structure generating
the permanent static magnetic field.
Using the
described method, a device can be manufactured which
generates a magnetic field adapted to the colour display
tube and which thus constitutes one unit as if it
were with the colour display tube. If desired colour
purity errors as well as convergence errors can be
eliminated by this method. The convergence errors visible
on the screen can be measured and expressed in
milimeters of horizontal and vertical errors. The
errors thus classified represent data whereby, using
magnetic poles of an intensity to be derived from the errors,
there can be determined a structure of a magnetic
multi-pole which generates a permanent magnetic field
adapted to the determined convergence errors.
As a
result of the generation of a desired magnetic
field by means of an auxiliary device and the derivation
of data therefrom, it is possible to determine a device
adapted to the relevant colour display tube.
Simultaneously, it is ensured that the convergence of
the electron beams can be effected.
A preferred
version of the method according to the invention is
characterized in that for the auxiliary device is used an
electromagnetic convergence unit which comprises a
number of coils wherethrough electrical currents are
conducted in order to generate a magnetic field
required for the convergence of the electron beams, the
values of the electrical currents producing the data
for determining an annular permanent magnetic
structure. Because the electrical currents whereby the
auxiliary device is actuated are characteristic of the
magnetic field generated, the intensity and the
position of the poles of the magnetic multi-poles to be
used for the colour display tube are determined by the
determination of the values of the electrical currents.
The
data obtained from the auxiliary device can be used
in various manners. The data from the auxiliary device
can be stored
in a memory, or the data from the auxiliary device can
be used immediately for controlling a magnetizing
unit which magnetizes an annular magnetizable structure.
Alternatively it is possible to convert the data
into a code; on the basis thereof an annular permanent
magnetic structure having a desired magnetic field
strength can be taken or composed from a set of already
magnetized structural parts. Obviously, the latter two
possibilities can be performed after the data have
been stored in a memory.
A simplification of the
method is achieved when the device is formed from a
magnetizable mass which is provided in the form of a ring
on at least one wall of the neck of the colour
display tube. The device to be magnetized is thus arranged
around the electron beams to be generated.
Subsequently, a construction which comprises the
auxiliary device and the magnetizing unit is arranged
around the neck of the colour display tube. The auxiliary
device is then adjusted, after which the construction
can possibly be displaced, so that the magnetizing unit
encloses the device. The magnetizing unit is
actuated on the basis of the data received from the
auxiliary device, and magnetizes the device.
In
order to make the construction of a magnetizing unit as
simple and as light as possible, it is advantageous to
polarize material of the structure to be magnetized
one area after the other by means of the magnetizing
unit. A suitable alternative of the method for which use
can be made of the described construction of the
magnetizing unit is characterized in that the device
consists of a non-magnetizable support and a number of
permanent magnetic bipoles. It was found that any
feasible magnetic field required for the static
convergence of electron beams in a neck of a colour
display tube can be comparatively simply generated using at
least one eight-pole electromagnetic convergence
unit. Similarly, any desired magnetic field can be
generated using a twelve-pole electromagnetic
convergence unit. It is to be noted that
electromagnetic convergence units have already been proposed
in U.S. Pat. No. 4,027,219.
The invention will be described in detail hereinafter with reference to a drawing.
FIG. 1 is a diagrammatic representation of a first version of the method according to the invention.
FIG. 2 is a diagrammatic representation of a second version of the method according to the invention.
FIG. 3 shows a preferred embodiment of an auxiliary device.
FIG. 4 is a side elevation of a first embodiment of a device manufactured using the method according to the invention.
FIG. 5 is a cross-sectional view of the embodiment shown in FIG. 4.
FIG. 6 is a side elevation of a further embodiment of a device manufactured using the method according to the invention.
FIG. 7 is a cross-sectional view of the device shown in FIG. 6.
FIG. 8 is a diagrammatic perspective view of a magnetizing device and a convergence unit arranged therein.
FIG. 9a is a cross-sectional view of a convergence unit manufactured using a method according to the invention.
FIG. 9b is a partial side elevation of part of a support of the convergence unit shown in FIG. 9a.
FIG. 9c shows a permanent magnetic structural part of the device shown in FIG. 9a.
The method according to the invention will be described with reference of FIG. 1. An electromagnetic
auxiliary device 5 is arranged around the neck 3 of
the colour display tube 1. The auxiliary device 5
will be described in detail with reference to FIG. 3.
Electrical currents which generate a magnetic field
are applied to the auxiliary device 5. When the
electrical currents are adjusted to the correct value, a
magnetic field adapted to the colour display tube 1 as
regards position and intensity is generated. The
electrical currents are measured by means of the
measuring unit 9. The electrical currents represent data
which completely describe the magnetic field generated by
the auxiliary device 5. The data are stored in a
memory 19 (for example, a ring core memory) in an
adapted form (digitally). The data can be extracted
from the memory 19 again for feeding a control unit 11.
The control unit 11 actuates a magnetizing unit 13. A
magnetic field is impressed on the device 15 arranged
inside the magnetizing unit 13 (shown to be arranged
outside this unit in FIG. 1), the said magnetic field
equalling the magnetic field generated by the auxiliary
device 5 at the area of the electron beams. The auxiliary
device 5 is then removed from the neck 3 and
replaced by the device 15.
The method is
suitable for the application of an automatic process
controller 17. The storage of the data in the memory 19,
the retrieval thereof, the determination and the feeding
of the data to the control unit 11 are operations
which are very well suitable for execution by an
automatic controller. Similarly, the process controller
17 can dispatch commands at the correct instants to
mechanisms which inter alia arrange the auxiliary
device 5 on the display tube 1, arrange the device 15 to
be magnetized in the magnetizing unit 13, remove the
auxiliary device 5 from the display tube 1, and arrange
the device 15 on the neck 3 of the display tube 1.
Besides these controlling functions, checking functions
can also be performed by the process controller, such
as the checking of:
the position of the display tube 1 with respect to the auxiliary device 5.
the determination of the number of data by the measuring unit 9.
the actuation of the magnetizing unit 13.
the position of the device 15 with respect to the display tube 1.The
method shown in FIG. 2 is an alternative to the
method described with reference to FIG. 1. The
auxiliary device 5 and the magnetizing unit 13 are
accommodated together in one construction 6. Before the
auxiliary device 5 and the magnetizing unit 13 are
arranged around the neck 3 of the colour display tube 1,
the as yet unmagnetized device 15 is arranged in a
desired position. The auxiliary device 5 is activated and
adjuste so that a magnetic field converging the
electron beams is produced. Subsequently, the measuring
unit 9 determines the necessary data whereby the
control unit 11 is adjusted. The auxiliary device 5
may be shifted so that the magnetizing unit 13 encloses
the device 15. After the current to the auxiliary
device 5 has been interrupted, the magnetizng unit 13 is
activated by the control unit 11. After magnetization
of the device 15, the auxiliary device 5 and the
magnetizing unit 13 are removed. A convergence unit which
has been exactly adjusted as regards position and
strength has then been arranged on the neck 3 of the
tube 1.

FIG. 3 more or less
diagrammatically shows an embodiment of an auxiliary device
5. The auxiliary device 5 comprises an annular
ferromagnetic core 21 having formed thereon eight pole
shoes a, b, c, d, e, f, g, and h which are situated
in one plane and radially orientated. Each pole
shoe has provided thereabout a winding wherethrough a
direct current I to be adjusted is to be conducted.
In
the space enclosed by the core 21 an eight-pole
static magnetic field is generated whose polarity and
intensity can be controlled. The value and the direction
of the direct currents Ia, Ib, Ic, Id, Ie, If, Ig and
Ih can be adjusted on the basis of the value and the
direction of the deviations of the electron beams to
be converged. The corrections required for achieving
colour purity and convergence can be derived from the
value and the direction of the direct currents Ia
and Ih which form the data from which the necessary
corrections are determined.
A similar embodiment can
be used for the magnetizing unit, but because the
electrical currents required for converging electron
beams are smaller than the currents required for
magnetizing the device, the conductors of the coils of
the magnetizing unit must be constructed in a
different manner which takes account the higher current
intensities. If a similar embodiment of the auxiliary
device has been made suitable for higher current
intensities, it can also operate at lower current
intensities. It follows that it is possible also to
use the magnetizing unit as the auxiliary device, which
is in one case connected to the measuring unit and in the
other case to the control unit.
FIG. 4 shows a partly cut-away neck 3 having an envelope 31 of a colour display tube, the flared portion
and the adjoining display screen not being shown.
At the end of the neck 3 there are provided contact
pins 33 to which cathodes and electrodes of the
system of electron guns 35 are connected. The device
15 for the static convergence of the electron beams
generated by the system of guns 35 consists of a support
15A of synthetic material and a ferrite ring 15B. On
the jacket surface of the support 15A is provided a
ridge 15c which extends in the longitudinal direction;
the ferrite ring 15B is provided with a slot which
co-operates therewith and which opens into the edge of
the ring on only one side, so that the ring 15B can be
secured to the carrier 15A in only one way. FIG. 5 is a
cross-sectional view which clearly shows the ridge 15C
and the slot of the device 15. The references used in
FIG. 5 correspond to those used in FIG. 4.
FIG. 6
shows the same portions of the neck 3 of a colour
display tube as FIG. 4. Instead of a support on which a
ferrite ring is secured, the device consists only of
a layer of ferrite 15 which is secured directly to the
inner wall 37 of the neck 3 by means of a binding
agent. This offers the advantage that a support which
requires space and material can be dispensed with. FIG. 7
is a cross-sectional view and illustrates the
simplicity of the device 15. The references used
correspond to the references of FIG. 6. The device 15
can also be mounted (not shown in the Figure) on the
rear of a deflection unit of the colour display tube.
It is alternatively possible to arrange the device on
grids or on the cathodes in the neck of the colour
display tube.
FIG. 8 diagrammatically shows a
magnetizing unit 13 whereby the device 15 arranged thereon
is magnetically polarized one location after the
other. The extent of the polarization is dependent of the
value and direction of the used direct current Im
and of the number of ampere-turns of the coil 41
arranged about the core of the magnetizing unit 13. The
core consists of two portions 43 and 45 which form a
substantially closed magnetic circuit. Between a
concave pole shoe 47 and a convex pole shoe 49 of the
core portions 43 and 45, respectively, there is a space
wherein a portion of the device 15 to be magnetized is
arranged. The concave and convex pole shoes 47 and
49 preferably are shaped to follow the curved faces 51
and 53 of the device substantially completely. In
order to enable easy arrangement and displacement of
the device between the pole shoes 47 and 49, the core
portions 43 and 45 are provided with ground contact
faces 55 and 57 which are perpendicular to each other.
The pole shoes 47
and 49 can be moved away from and towards each other,
the core portions 43 and 45 always returning to the
same position relative to each other due to the
faces 55 and 57 perpendicularly extending to each
other. At the same time, the magnetic contact resistance
at the faces 55 snd 57 is low and constant, so that the
necessary unambiguous relationship between the
current Im and the magnetic field generated in the core
is ensured.
FIGS. 9a, b and c show a preferred embodiment and details of a static convergence device 15. The device 15
consists of a support 61 of synthetic material, for
example, polycarbonate, wherein eight ferromagnetic
discs (or "inserts") 63 are equidistantly arranged
along the circumference. It will be obvious that
this embodiment is particularly suitable for being
actuated in a magnetizing unit as shown in FIG. 8. The
holes 65 provided in the support 61 are slightly
elliptical so as to lock the capsules 63 firmly in
the holes 65. To this end, the width b is chosen to be
slightly smaller than the height h which equals the
diameter d of the round discs (or "inserts") 63. The
narrow portions 67 of the support 61 with clamp the
disc 63 in the hole 65 due to their elastic action. It
is, of course, possible to magnetize the disc 63
before they are arranged in the support 61; the
sequence in which the disc 63 are arranged in the
support 61 should then be carefully checked.
If a
method is used where the most suitable structure is
selected from a series of permanent magnetic structures
on the basis of the adjusting data, it is
advantageous to compose this structure from a number of
permanent rings.
This will be illustrated on the basis of an example
involving superimposition of a four-pole field and a
six-pole field. Assume that the magnetic fields can
each have M different intensities, and that the on field
can occupy N different positions with respect to the
other field. If the magnetic structure consists of
one permanent magnetic ring, the series from which
selection can be made consists of M×M×N rings. If the
structure consists of two rings, the series comprises M+M
rings, but it should then be possible for the one ring
to be arranged in N different positions with respect
to the other ring. If the static convergence device
is composed as shown in FIG. 9a, b and c or similar,
only M kinds of structural parts (discs) having a
different magnetical intensity are required for achieving
any desired structure.

Getter connected to cathode ray tube high voltage contact:Disclosed is a picture display tube comprising an envelope having a display window, a cone and a neck.
An electrode system to generate at least one
electron beam is mounted in the neck and an
electrical resistive layer extends over an internal
wall portion of the envelope to a point near the electrode
system. The tube comprises a getter which is
detachably secured to a connecting member projecting
internally from the wall of the tube at a location
remote from the electrode system by means of a resilient
connection strip. The portion of the connection member
projecting from the tube wall has a gradually
widening end having a largest transverse dimension D
and a smallest transverse dimension d and the connection
strip of the getter has a first aperture whose
dimensions are larger than the dimension D. The first
aperture debouches via a passage of width b into a
second aperture of dimensions A in a manner such that
D>A>b>d, so that the gradually
widening end of the connecting member in cooperation
with the said second aperture forms a detachable
coupling.

1. A display
tube comprising an envelope having a conical portion
terminating in a generally cylindrical neck and a
window portion secured to the end of said conical
portion opposite said neck and having a display screen on
the inner surface thereof, an electrode system
positioned in said neck for generating at least one
electron beam directed onto said display screen, an
electrically conductive layer extending between said
display screen and said electrode system over the inner
surface of said conical portion, at least a portion
of said layer near said electrode system being an
electrical resistive layer and electrically connected
to the conductive layer, a high voltage contact
provided in said conical portion between said window
portion and said electrode system, a getter and means for
detachably mounting, in said envelope, said getter
inserted into said conical portion through said neck
after said window portion is secured to said conical
portion and prior to positioning said electrode system
in said neck, said mounting means including a
connecting member affixed to a wall of said conical
portion and projecting into the interior of said
envelope, said connecting member having a gradually
widening end with a largest transverse dimension D and
a smallest transverse dimension d, and a resilient
metal strip affixed to said getter, said strip having a
first aperture of a dimension larger than said
dimension D, a second aperture of dimension A, and
an opening of width b extending between said first and
second apertures in a manner such that
D>A>b>d, so that said end of said
connecting member in cooperation with said second
aperture form a coupling for detachably mounting said
getter in said envelope. 2. A picture display tube as
claimed in claim 1, wherein the portion of the
connecting member projecting from the tube wall widens
conically. 3. A picture display tube as claimed in claim
1, wherein the portion of the connecting member
projecting from the tube wall widens spherically. 4. A
picture display tube as claimed in claim 1, wherein
the portion of the connecting member projecting from the
tube wall widens in the form of a pyramid. 5. A picture
display tube as claimed in claim 1 wherein said metal
strip affixed to the getter has an indentation at
the region of the second aperture. 6. A picture
display tube as claimed in claim 5 wherein the shape of
said indentation corresponds to the shape of the
gradually widening end of the connecting member. 7. A
picture display tube as claimed in claim 1, wherein the
connection strip of the getter is locked against
rotation with respect to the connecting member. 8. A
picture display tube as claimed in claim 1 wherein the
connecting member is secured to the high voltage
contact. 9. A picture display tube as claimed in claim 8
wherein the connecting member and the high voltage
contact are integral and are made from sheet material.
10. A device for connecting a getter in a picture
display tube in which the getter is inserted via the
tube neck and is secured so as to be detachable to a
connection member projecting internally from the tube
wall by means of a resilient connection strip,
characterized in that the device comprises a strip of
resilient material which at one end is secured to a rigid
member and at the other end has a holder on which a
number of studs are present between which the
connection strip of the getter can be clamped
temporarily and which holder comprises means to detach
the connection strip from the holder, which device has
an abutment limiting the depth of insertion of the
strip in the tube and furthermore has a cable which is
guided along the strip and is secured near the holder to
bend the strip and thus to transport the getter which
is temporarily secured to the holder towards the
connection member projecting internally from the tube
wall.

Description:

The invention relates to
a picture display tube comprising an envelope
including a display screen, an electrode system to
generate at least one electron beam directed onto the
display screen, an electrically conductive layer which
extends at least between the display screen and the
electrode system over the inner surface of the envelope.
At least the portion of the conductive layer situated
near the electrode system is an electrical resistive
layer. The tube further comprises a high voltage
contact which is provided in the envelope between the
display screen and the electrode system and which is
electrically connected to the conductive layer, and a
getter which is secured to a connection member
projecting internally from the tube wall by means of a
resilient metal strip.
Such a picture display tube is disclosed in British patent specification No. 1,226,728.
As
a result of the large voltage differences between
certain electrodes of the electrode system,
electrical flashovers in the tube may occur which
are associated with currents rising rapidly in time and
reaching high values. As a result of this, damage may be
done, in particular, to semiconductor components in
the electronic circuit of the television receiver
via inductive or capacitive coupling. A known solution
for avoiding such damage is to provide an electrically
resistive layer on an internal wall portion of the
tube envelope near the electrode system. The result of
this solution, however, is that the getter usually
connected to the electrode system by means of a metal strip
has to be secured elsewhere in the tube to prevent the
gettering material released from the getter by
heating from depositing on and shortcircuiting the
resistive layer or prevent the layer from being
shortcircuited by the metal strip. Thus the getter should
be mounted in the tube at a location remote from the
electrode system.
In FIG. 3 of the
above-mentioned British patent specification the getter is
secured to the high voltage contact. The getter is
connected to the contact prior to securing the glass cone to
the glass window of the tube. An advantage of this
method is that the getter is mounted in the tube during a
phase of the manufacturing process of the tube when
the location in the tube at which the getter is to be
mounted is still readily accessible. The detrimental
effects of gases and vapours on the getter during
subsequent phases in the manufacturing process can be
avoided by using a protective getter or a chemically
resistant getter.
The method disclosed in the
British patent specification would be satisfactory if
there were no need at all for mounting a getter in the
tube after the cone and the window are secured to
each other as is the case with black-and-white display
tubes. However, during manufacture of colour tubes the
envelope is stored for some time after the window is
secured to the cone. In that case, therefore, it is
undesirable to mount the getter at the time the tube
envelope is assembled. Furthermore if the tube has to be
repaired it has to be provided with a new getter.
It
is the object of the invention to provide a picture
display tube in which a getter can be introduced
through the neck of the tube and in which, in a
location remote from the electrode system, the tube is
provided with a connection member to which the getter can
be easily secured, as well as easily detached.
According
to the invention, a picture display tube of the
kind mentioned in the preamble is provided with a
connecting member which projects from the tube wall. The
connecting member has a gradually widening end having a
largest transverse dimension D and a smallest
transverse dimension d. The getter has a metal
connection strip with a first aperture whose dimensions are
larger than the largest transverse dimension D. The
first aperture debouches via a passage of width b into a
second aperture having dimensions A, in a manner
such that D>A>b>d, so that the
gradually widening end of the connection member in
cooperation with the second aperture forms a detachable
coupling.
The getter is secured by inserting the
widening end of the connecting member through the
first aperture in the connecting strip and then moving
the connection strip in its longitudinal direction in a
manner such that the second aperture is made to
cooperate with the widening end of the connecting
member. The coupling thus produced is locked in that
the connection strip bears on the tube wall on either
side of the second aperture and, as a result of the
resilience in the strip, the strip is pressed against
the widening end of the connection member at the area of
the second aperture. It has been found that a good
coupling between the connection member and the
connection strip is obtained even with low resilience of
the strip. Hence no large resilient forces need be
overcome for producing the coupling. As a result of this,
the auxiliary tool for mounting the getter can be of
an extremely simple construction and minimizing the
possibility of damage to the tube during mounting of
the getter. The removal of the getter during repair
of the tube can also be carried out in an extremely simple
manner and without exerting great forces with the
coupling mechanism of the invention.
The
gradually widening end of the connection member may
have several shapes. The end preferably is in the form of
a sphere, a cone or a pyramid. In a further
embodiment according to the invention the connection
strip has a deepened portion or an indentation at the
region of the second aperture so that an extra locking
of the coupling is obtained. The shape of the indentation
may correspond to the shape of the gradually
widening end of the connection member.
In the
latter arrangement and with a connection member widening
in the form of a pyramid, the strip may also be
locked against rotation with respect to the connection
member. Locking against rotation is alternatively
possible by providing the widening end of the
connection member with at least one flattened portion
which cooperates with a straight edge of the second
aperture.
The connection member is preferably
secured to the high voltage contact provided in the
tube wall so that with the insertion of the high
voltage contact the connection member for the getter is also
obtained. According to a further embodiment of the
invention the connection member with the high voltage
contact constitutes one assembly of sheet material.
The invention will now be described in greater detail with reference to the drawing in which:
FIG. 1 is a sectional view of a colour television display tube with a getter according to the invention,
FIG. 2 shows on an enlarged scale the manner in which the getter is secured in the display tube shown in FIG. 1,
FIGS.
3, 3A and 3B are sectional views of embodiments of a
connection member according to the invention
secured to the high voltage contact,
FIG. 4 is a plan view of a getter having a connection strip according to the invention,
FIG. 5 is a sectional view of an embodiment of a connection construction according to the invention,
FIG. 6 is a sectional view of a connecting member forming one assembly with the high voltage contact, and
FIGS. 7, 7A and 7B show an auxiliary tool for mounting a getter according to the invention in the tube.
The tube, shown
in FIG. 1 in a vertical sectional view, comprises a
glass envelope having a display window 1, a cone 2
and a neck 3. An electrode system 4 for generating
three electron beams 5, 6 and 7 is mounted in the neck
3. The electron beams 5, 6 and 7 are generated in one
plane, in this case normal to the plane of the
drawing, and are directed onto a display screen 8
provided internally on the display window 1 and
consisting of a large number of phosphor strips
luminescing in red, green and blue whose longitudinal
direction is parallel to the plane of the drawing. On
their way to the display screen 8, the electron beams 5,
6 and 7 are deflected over the display screen 8 by
means of a number of deflection coils 9 arranged
coaxially around the tube axis and pass through a colour
selection electrode 10 consisting of a metal plate
having elongate apertures 11 whose longitudinal direction
is also parallel to the plane of the drawing. The
three electron beams 5, 6 and 7 pass through the
apertures 11 at a small angle to each other and
consequently each impinges only upon phosphor strips of
one colour. The tube furthermore comprises an inner
screening cone 12 screens which the electron beams 5, 6
and 7 from the earth's magnetic field. The inner wall
of the tube is coated with an electrically conductive
layer 13 with a portion 14 extending from the neck-cone
transition in the neck 3 consisting of an
electrically resistive material which is composed of a
mixture of approximately 6 parts by weight of ferric
oxide and 1 part by weight of graphite and 2.5 parts by
weight of potassium silicate. The layer 13, which may
alternatively consist of an electrically resistive
layer, is connected to a high voltage contact 15
provided in the tube wall and is further connected, via
contact springs 16, to the colour selection electrode
10 and the display screen 8 and, via contact springs
17, to the last electrode of the electrode system 4.
As
is known, after evacuation of the tube a layer of
gettering material of, for example, barium, strontium,
calcium or magnesium is deposited on the tube wall so as
to getter the residual gases remained in the tube. In
conventional display tubes, the gettering device from
which the gettering material is released by heating,
is connected to the electrode system either directly
or by means of a metal strip. As already stated, this
conventional mounting arrangement cannot be used in a
display tube having a resistive layer. As shown in FIG.
1, according to the invention, the getter 18 is mounted
in the tube by means of a connection strip 19 at a
location remote from the electrode system 4. The
getter is detachably secured to a connection member
welded to the high voltage contact 15 by using a
mounting arrangement described hereinafter with reference
to FIG. 2. This figure shows the wall portion of the
cone 2 in which the high voltage contact 15 is sealed.
The high voltage contact 15 has a connection member
which extends into the tube cavity and which is in
the form of a pin 20 which at its free end widens in the
form of a cone and has a largest transverse dimension
D and a smallest transverse dimension d, as shown in
FIG. 3. As shown in FIG. 2 the getter 18 comprises a
metal holder 21 which is welded to the metal connection
strip 19. The strip 19 has a first aperture 22 whose
dimensions are larger than the transverse dimension D. The
aperture 22 communicates via a passage 23 with a
second aperture 24 which is smaller than the
transverse dimension D but is larger than the transverse
dimension d. The width of the passage 23 is slightly
larger than the dimension d but is smaller than the
aperture 24. This is illustrated in the plan view in
FIG. 4 of a getter 28 and a connection strip 29. The strip
has a first aperture 32, a passage 33 and a second
aperture 34. Due to the resilience of the connection
strip 19, which is pre-bent according to the broken lines
25, (shown in FIG. 2), the strip 19 presses against
the conically widening end of the pin 20 at the area
of the second aperture 24 with which the coupling of
the strip 19 and the pin 20 is produced. Possible
rotation of the strip 19 about the pin 20 can be
prevented, for example, by providing the widening end
of the pin 20 with at least one flattened portion as
shown in FIG. 3 by the broken line 26 and providing
the second aperture 24 with a straight edge cooperating
with the flattened portion.
Instead of a
conically widening end, other shapes are also possible, for
example, the spherically widening end 27 of the
connection member shown in FIG. 3A, or the end 30
widening in the form of a pyramid as shown in FIG. 3B.
Furthermore it is not necessary to secure the
connection member to the high voltage contact. The
connection member may also be inserted independently in
the tube wall.
FIG. 5 shows a getter structure in which the connection strip 39 has an indentation 40 at the region of the
second aperture 44. As a result of this, the
coupling between the connection strip 39 and the
connection member 41 is additionally locked.
Otherwise, the strip 39 again has a first aperture 42 which
debouches via a passage 43 into the second aperture
44, analogously to the construction shown in FIG. 4.
FIG.
6 shows a high voltage contact 50 having a
connection member 51 integral therewith. The assembly
is manufactured from sheet material and obtained by deep
drawing. This construction which has been manufactured
from one piece has the advantage that no welding
operation need be carried out which might damage the
high voltage contact.
FIG. 7 shows a possible
embodiment of a device for inserting the getter through
the neck of the tube and mounting it in the tube. The
device comprises a resilient metal strip 60 which at
one end has a metal holder 61 provided with an
elongated aperture 62. The other end of the strip 60 is
secured to a rigid tube 63 having a handle 64. A pull
cable 65 connected at one end to the holder 61 is guided
along the strip 60 by means of cable guides 66 and at
the other end is attached to a handle 67 rotatably
secured to the tube 63. The resilient strip 60 is bent
by tensioning the cable 65 by means of the handle 67. A
stud 68 is rotatably arranged about a shaft 69 in
the aperture 62 of the holder 61. A second pull cable 70,
which is also guided along the strip 60 with a small
amount of play is rotatably secured at one end to a
second handle 71 connected to the tube 63 and is secured
to the stud 68 at its other end. By tensioning the
pull cable 70 by means of the handle 71, the stud 68
rotates about the shaft 69 releasing a getter secured
to the holder 61.
FIG. 7A shows the getter 28
of FIG. 4 with connection strip 29 in a position in
which it is mounted on the holder 61. The connection strip
29 has four abutment edges 35 with which the strip 29
can be tensioned between four studs 72 on the holder
61. In the position shown in FIG. 7A, the getter 28
can be positioned in its place via the still open neck
3 of the tube shown in FIG. 1. This is done as
follows. The resilient strip 60 of the getter insertion
apparatus shown in FIG. 7 is inserted into the neck 3
of the tube a distance such that the abutment member 73
bears against the open end of the tube neck 3. The
pull cable 65 is then tensioned so that the strip 60
bends and the holder 61 is moved towards the high
voltage contact 15 with the connection member 20. Access
to the high voltage contact is provided via a
slot-shaped recess 80 in the magnetic screening cone 12,
as shown in FIG. 1. The location of the abutment
number 73 on the insertion apparatus is such that in
the bent condition of the strip 60, the aperture 32
provided in the connection strip 29 corresponds to
the location of the connection member 20 so that, when
the strip 60 is bent, the connection strip 29 slides
over the widening end of the connection member 20. The
strip 29 is then moved in its longitudinal direction
until the second aperture 34 coincides with the
connection member 20. In this phase of the method, the
connection strip 29 is detached from the holder 61 by
tensioning the cable 70 so that the stud 68 rotates
and the connection strip 29 is pressed between the studs
72. Due to the resilience of the connection strip 29,
the strip presses against the gradually widening end of
the connection member 20 at the area of the aperture
34. Thus the coupling of the strip 29 and the
connection member 20 is produced in the manner as shown in
FIG. 2 or FIG. 5.
The principle of inserting and
securing a getter in the tube has been explained with
reference to a manually operated apparatus. Of
course, the operation of the apparatus can be mechanized.
Detaching the connection strip of the getter from
the holder can furthermore be realised in ways differing
from that with the stud 68. For example, as shown in
FIG. 7B, the holder 90 may consist of two portions 91
and 92 pivoting about a shaft 83. To detach the
connection strip of the getter, the part 92 of the
holder 90 is tilted in the direction of the arrow 94.
According to another possibility, the holder can be
made detachable by a construction in which the parts 91 and
92 are drawn apart in the longitudinal direction of
the holder.

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Resisting the tide of post-modernity may be difficult, but I will attempt it anyway.

Your choice.........Live or DIE.That indeed is where your liberty lies.

IMPORTANT NOTE: - FRANK SHARP obsoletetellyemuseum.blogspot.comwas founded as a public free WEB Museum to all kind of people and amateur and professional CRT TELEVISION Lovers who enjoy using and/or preserving - restoring vintage CRT Televisions sets, or only curious public who was unaware of that kind of technolgy of the past. The purpose is to provide information about vintage Television Receivers Publicy on the WEB that is generally difficult to locate; all this as a important milestone general worldwide reference for the future, globally in the public interest.obsoletetellyemuseum.blogspot.com does not provide support or parts for any apparatus on this site nor do we represent any manufacturer listed on this site in any way. Catalogs, manuals and any other literature that is available on this site is made available for a historical record only. Please remember that safety standards have changed over the years and information in old manuals as well as the old Television receivers themselves may not meet modern standards. It is up to the individual user to use good judgment and to safely operate old machinery. The obsoletetellyemuseum.blogspot.com web site will assume NO responsibilities for damages or injuries resulting from information obtained from this site. No offer to sell or license — Nothing in this site/Blog may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights.

Many topics are permanent, so may be updated to any material, for add or correct info.

Sure Fun Times, A working TV Discovered with a CRT Oscilloscope !

Safety Hazards:

------------------------------------------------------Safety Hazards in Radio and TV Repair,------------------------------------------------------

People who believe they can conquer nature are clueless that the laws of nature are a precondition of their existence. Their weapon is a miserable idea.When man attempts to rebel against the iron logic of Nature, he comes into struggle with the principles to which he himself owes his existence as a man. And this attack must lead to his own doom.

Anyone attempting to repair any electronic equipment who does not fully understand the shock hazards, as well as the fire hazards associated with working with electronic equipment, should not attempt such procedures! Improperly attempted repair can kill you and burn down your house.Devices that plug into the wall can produce a very lethal electric shock as well cause a fire from incorrect or careless repairs both during servicing or later on.Improper repair of battery operated devices can also result in bad consequences for you, the device, and any equipment attached to it.

Why some people do repairs themselved then? If you can do the repairs yourself, the equation changes dramatically asyour parts costs will be 1/2 to 1/4 of what a professional will chargeand of course your time is free. The educational aspects may also beappealing. You also will learn a lot in the process.

Consumer electronic equipment like TVs, computer monitors, microwave ovens, and electronic flash units, use voltages at power levels that are potentially lethal. Even more so for industrial equipment like lasers and anything else that is either connected to the power line, or uses or generates high voltage.

Normally, these devices are safely enclosed to prevent accidental contact. However, when troubleshooting, testing, making adjustments, and during repair procedures, the cabinet will likely be open and/or safety interlocks may be defeated. Home-built or modified equipment, despite all warnings and recommendations to the contrary - could exist in this state for extended periods of time - or indefinitely.

Depending on overall conditions and your general state of health, there is a wide variation of voltage, current, and total energy levels that can kill.

Microwave ovens in particular are probably THE most dangerous household appliance to service. There is high voltage - up to 5,000 V or more - at high current - more than an amp may be available momentarily. This is an instantly lethal combination.

TVs and monitors may have up to 35 kV on the CRTbut the current isn't low - like a wrong legend saying a "couple of milliamps" but relatively high because of the boost circuit technology and transformer design. However, the CRT capacitance can hold a painful charge for a long time. In addition, portions of the circuitry of TVs and monitors as well as all other devices that plug into the wall socket are line connected.This is actually even more dangerous than the high voltage due to the greater current available - and a few hundred volts can make you just as dead as 35 kV!

Electronic flash units and strobe lights, and pulsed lasers have large energy storage capacitors which alone can deliver a lethal charge - long after the power has been removed. This applies to some extent even to those little disposable pocket cameras with flash which look so innocent being powered from a single 1.5 V AA battery. Don't be fooled - they are designed without any bleeder so the flash can be ready for use without draining the battery!

Even some portions of apparently harmless devices like VCRs and CD players - or vacuum cleaners and toasters - can be hazardous (though the live parts may be insulated or protected - but don't count on it!

This information also applies when working on other high voltage or line connected devices like Tesla Coils, Jacobs Ladders, plasma spheres, gigawatt lasers, hot and cold fusion generators, cyclotrons and other particle accelerators, as well as other popular hobby type projects. :-)

In addition, read the relevant sections of the document for your particular equipment for additional electrical safety considerations as well as non-electrical hazards like microwave radiation or laser light. Only the most common types of equipment are discussed in the safety guidelines, below.

SAFETY guidelines:

These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in themselves, may cause collateral damage. There are likely to be many sharp edges and points inside from various things like stamped sheet metal shields and and the cut ends of component leads on the solder side of printed wiring boards in this type of equipment. In addition, the reflex may result in contact with other electrically live parts and further unfortunate consequences.

The purpose of this set of guidelines is not to frighten you but rather to make you aware of the appropriate precautions. Repair of TVs, monitors, microwave ovens, and other consumer and industrial equipment can be both rewarding and economical. Just be sure that it is also safe!

Don't work alone - in the event of an emergency another person's presence may be essential.

Always keep one hand in your pocket when anywhere around a powered line-connected or high voltage system.

Wear rubber bottom shoes or sneakers. An insulated floor is better than metal or bare concrete but this may be outside of your control. A rubber mat should be an acceptable substitute but a carpet, not matter how thick, may not be a particularly good insulator.

Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts.

Set up your work area away from possible grounds that you may accidentally contact.

Have a fire extinguisher rated for electrical fires readily accessible in a location that won't get blocked should something burst into flames.

Use a dust mask when cleaning inside electronic equipment and appliances, particularly TVs, monitors, vacuum cleaners, and other dust collectors.

Know your equipment: TVs and monitors may use parts of the metal chassis as ground return yet the chassis may be electrically live with respect to the earth ground of the AC line. Microwave ovens use the chassis as ground return for the high voltage. In addition, do not assume that the chassis is a suitable ground for your test equipment!

If circuit boards need to be removed from their mountings, put insulating material between the boards and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood.

If you need to probe, solder, or otherwise touch circuits with power off, discharge (across) large power supply filter capacitors with a 2 W or greater resistor of 100 to 500 ohms/V approximate value (e.g., for a 200 V capacitor, use a 20K to 100K ohm resistor). Monitor while discharging and/or verify that there is no residual charge with a suitable voltmeter. In a TV or monitor, if you are removing the high voltage connection to the CRT (to replace the flyback transformer for example) first discharge the CRT contact (under the insulating cup at the end of the fat red wire). Use a 1M to 10M ohm 1W or greater wattage resistor on the end of an insulating stick or the probe of a high voltage meter. Discharge to the metal frame which is connected to the outside of the CRT.

For TVs and monitors in particular, there is the additional danger of CRT implosion - take care not to bang the CRT envelope with your tools. An implosion will scatter shards of glass at high velocity in every direction. There is several tons of force attempting to crush the typical CRT. Always wear eye protection. While the actual chance of a violent implosion is relatively small, why take chances? (However, breaking the relatively fragile neck off the CRT WILL be embarrassing at the very least.)

Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations.

If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return so that you need to only probe with one hand.

Perform as many tests as possible with power off and the equipment unplugged. For example, the semiconductors in the power supply section of a TV or monitor can be tested for short circuits with an ohmmeter.

Provide a reliable means of warning that power is applied and that high voltage filter capacitor(s) still hold a charge during servicing. For example, solder a neon indicator lamp (e.g., an NE2 in series with a 100K ohm resistor) across the line input and a super high brightness LEDs in series with 100K, 1 W resistors across the main filter capacitor(s).

Use an isolation transformer if there is any chance of contacting line connected circuits. A Variac(tm) (variable autotransformer) is not an isolation transformer! However, the combination of a Variac and isolation transformer maintains the safety benefits and is a very versatile device. See the document "Repair Briefs, An Introduction", available at this site, for more details.

The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but may not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. (Note however, that, a GFCI may nuisance trip at power-on or at other random times due to leakage paths (like your scope probe ground) or the highly capacitive or inductive input characteristics of line powered equipment.) A GFCI is also a relatively complex active device which may not be designed for repeated tripping - you are depending on some action to be taken (and bad things happen if it doesn't!) - unlike the passive nature of an isolation transformer. A fuse or circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. However, these devices may save your scope probe ground wire should you accidentally connect it to a live chassis.

When handling static sensitive components, an anti-static wrist strap is recommended. However, it should be constructed of high resistance materials with a high resistance path between you and the chassis (greater than 100K ohms). Never use metallic conductors as you would then become an excellent path to ground for line current or risk amputating your hand at the wrist when you accidentally contacted that 1000 A welder supply!

Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity.

Finally, never assume anything without checking it out for yourself! Don't take shortcuts!

Many people who mistakenly feel that ‘old technology’ is somehow more user-friendly, in some strange way automatically good - merely because it is old. Don’t be fooled! Approach old equipment with an open and alert mind and realise that a hot chassis, or a resistor line cord, or asbestos insulation, or selenium rectifiers require much more thought and consideration for safety.

Live chassis are indiscriminate in whom they kill and even if you are a thoughtful, careful kind of person, that doesn’t mean the last person who handled the set was.

Vintage radio and television receivers use 'live chassis' techniques, in which the chassis is connected directly to one side of the incoming mains supply. This means they can be lethal to carry out repair or servicing work on, unless the appropriate safety measures are in place.

Another thing about live-chassis sets - live spindles. We’ve touched on this already but it’s worth making the point once more. The shafts of switches and potentiometers fixed to the chassis may well be at chassis potential and thus live. The bakelite or wood cabinet is insulated but these shafts are not, and if someone lost the proper grub screw and replaced a knob using a cheesehead screw, the next person to grip that knob may get a dose of 250 volts. Originally these grub screws were sealed and embedded in wax but you cannot rely on subsequent tinkerers having the same high standards.

Even in more orthodox apparatus standards of insulation were not always as high as they are now. Soldered connections to HT and mains wiring should always have rubber or plastic sleeving but in times gone by this was often omitted (or it may since have perished). Beware too of kinked and frayed braiding on cloth-covered mains cords, particularly when the cord has a dropper conductor.

If you are not satisfied that you fully understand the risks involved in this sort of work, do not proceed any further. Instead seek advice and assistance from a competent technician or engineer.

Whenever you acquire a new treasure there's always a terrific temptation to try it out. With mains-driven equipment that means plugging it in and seeing if it works. Well don't, not until you have made some quick checks.

Before contemplating connecting any unknown receiver to the mains supply, spend a little time inspecting it for signs of missing or loose parts, blown fuses, overheating or even fire damage. Use a meter to check obvious points to ensure no short circuit exists (e.g. across the mains input). If you then decide to apply power keep clear but be observant since an elderly electrolytic might explode! This can be avoided if you can apply power gradually through a variac. Auto-transformers are handy for supplying reduced power to sets being repaired but they are not a substitute for a proper isolation transformer!

If you are working with electricity and your work area has a concrete floor, a rubber mat is essential, particularly during damp weather! Where possible try to arrange a neat working area away from water or central heating pipes. For safety try to arrange that this area is separate from the area occupied by your family. This is emphasised because inadvertently rushing to answer a telephone you might just leave a TV chassis connected to a supply and curious little fingers know nothing of the dangers of electricity - or, for that matter - the lethal vacuum encased within every picture tube!

Many younger enthusiasts may not be aware of the dangers of mishandling tubes, in particular the old round types found in early TVs. When handling these tubes eye protection should be worn and tubes must not be left lying around, they must be stored in boxes. The glass is surprising fragile and can implode without any provocation or warning. Bits of glass flying around at high speed can be deadly. The notes following are inspired by Malcolm Burrell again.

Picture tubes are perhaps one of the most hazardous items in any TV receiver. This is because most are of glass construction and contain a very high vacuum. If you measured the total area of glass in any picture tube then estimated the pressure of air upon it at 14.7lb. per square inch, you would discover that the total pressure upon the device could amount to several tons! Fracturing the glass suddenly would result in an extremely rapid implosion such that fragments of glass, metal and toxic chemicals would be scattered over a wide area, probably causing injury to anyone in close proximity. In modern workshops it is now a rule that protective goggles are worn when handling picture tubes.

The weakest point in most picture tubes is where the thin glass neck containing the electron gun is joined to the bowl. It is therefore essential that you refrain from handling the tube by its neck alone. Once a tube is removed from the receiver hold it vertically with the neck uppermost and one hand beneath the screen with the other steadying the device by the neck.With larger devices it is sometimes easier to grip the peripheral of the screen with both hands.

Until the advent of reinforced picture tubes, most were mounted in the cabinet or on the TV chassis by some form of metal band clamped around the face.Never support the weight of the tube by this band since it has been known for the tube to slide out! Some of the larger tubes are extremely heavy. It may, therefore, be easier to enlist assistance.

Before starting to remove a tube, first discharge the final anode connection to the chassis metalwork and preferably connect a shorting lead to this connection whilst you are working. It might be convenient to keep a spare piece of EHT cable with a crocodile clip at one end and a final anode connector at the other.

Exercise care when removing picture tubes from elderly equipment. You may find that the deflection coils have become stuck to the neck. It is extremely dangerous to use a screwdriver prise them away. Gently heating with a hairdryer or soaking in methylated spirit is safer.

Disposal of picture tubes also requires care. Unless rendered safe they should never be placed in dustbins or skips. Many engineers swipe the necks off tubes in cavalier fashion using a broom handle but this is not recommended. A safer method is to make a hole in the side of a stout carton, preferably one designed to hold a picture tube. The tube is placed in the carton and the neck broken using a broom handle. The carton should then be clearly labelled that it contains chemicals and broken glass!

Therefore people who believe they can conquer nature are clueless that the laws of nature are a precondition of their existence. Their weapon is a miserable idea.When man attempts to rebel against the iron logic of Nature, he comes into struggle with the principles to which he himself owes his existence as a man. And this attack must lead to his own doom.

Think for yourself. Otherwise you have to believe what other people tell you.

For most people thinking is a matter of fortune.A society based on individualism is an oxymoron.Freedom is at first the freedom to starve.A wise fool speaks, because he has something to say.A fool speaks, because he has to say something.A wise fool is silent, because there is nothing to say.A fool is silent, because he has nothing to say.

Resist or regretWork for what's good for our people

Help stem the dark tideStand tall or be beat downFight back or die

The man who does not exercise the first law of nature—that of self preservation — is not worthy of living and breathing the breath of life.

We now live in a nation where doctors destroy health, lawyers destroy justice, universities destroy knowledge, governments destroy freedom, the press destroys information, religion destroys morals and our banks destroy the economy.The globalist argument is that if only we erase distinctions, obliterate identities, put everyone on a level playing field, etc.. we can eliminate war and everyone can be so prosperous and efficient, such great cogs in a well-oiled global machine.There will be no more historical grievances because people will no longer even care, they'll have no connection to the past, no foolish pride in past accomplishments of people totally unrelated to them.A globalized culture, no borders, everyone a citizen of the world.Know this: I will never acquiesce to this corrupt, inhuman, Borg-like vision. The dangerous lunatics who push us towards their globalized "utopia" are my enemy. How exactly all this will play out, whether through wars, or whether we can thwart the globalist agenda peacefully (this is my hope of course) I don't know. But I do know that unless people are willing to fight and die, globalism will win out in the end.The actual crimes committed by the EU against the European peoples are directly in violation of the 1948 UN genocide convention, Article II: (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; (d) Imposing measures intended to prevent births within the group; (e) Forcibly transferring children of the group to another group.* The man who does not exercise the first law of nature—that of self preservation — is not worthy of living and breathing the breath of life.

TELEVISION HISTORY IN BRIEF

Television history

At 1928 Baird transmits from London to New York, using his mechanical system.with 30 vertical lines. By 1930 it was clear that mechanical television systems could never produce the picture quality required for commercial success. For this reason mechanical system was rapidly succeeded by the electronic TV systems. The first all-electronic American systems in 1932 used only 120 scanning lines at 24 frames per second Since the mid-1930s picture repetition frequency (field rate or frame rate) has been the same as the mains frequency, either 50 or 60Hz according to the frequency used in each country. This is for two very good reasons. Studio lighting generally uses alternating current lamps and if these were not synchronised with the field frequency, an unwelcome strobe effect could appear on TV pictures. Secondly, in days gone by, the smoothing of power supply circuits in TV receivers was not as good as it is today and ripple superimposed on the DC could cause visual interference. If the picture was locked to the mains frequency, this interference would at least be static on the screen and thus less obtrusive.To determine what electronic system to use, the BBC sponsored trial broadcasts by two systems, one by Baird, with 240 lines, and one by EMI with 405 lines. Scheduled electronic television broadcasting began in England in 1936 using 405-line system (lasted until the 1980s in the UK). Germany made their forst TV broadcasts at 1936 olympics using 180-line TV system. Germany also made their TV broadcasts by the fall of 1937 using a 441-line system. Also fFrance tested TV (455 line system). RCA introduced electronic television to the U. S. at the 1939 World's Fair,and began regularly scheduled broadcasting at the same time (525 line system).In 1940 the USA established its 525-line standard. At year 1941 the 525-line standard, still in use today in USA, was adopted.Russia also produced TV sets before the war (240 and 343 line systems).World War Two interrupted the development of television. Immediately after World War Two production of TV sets started in the U.S-In USA there was TV broadcasts and few throusand receivers at 1945. In the early 1950s, two competing color TV systems emerged: CBS sequential color (used color wheel) and RCA dot sequential system. At 1953 color broadcasting officially arrives in the U.S. on Dec. 17, when FCC approves modified version of an RCA system.It calls this new RCA color system "NTSC" color. The first NTSC color TVs were on the marker at 1954.In Europe the TV broadcasts started to use experiment using 625 line system 1950s. This standard is used nowadays throughout Europe. France also tried 819 line system at the same time (this system was in use to 1980s). The rest of Europe opted for 625 lines, a system devised in 1946 by two German engineers, M??ller and Urtel (it appears that the Russians came up independently with a very similar system). The use of PAL color standard started at around 1967 and is still in use. The SECAM color system (used in France) testing started also at 1967. The TV broadcasting history has not ended. The newst thign is digital television. It is expected that terrestrial television will open up billion-dollar opportunities for those companies and organisations best prepared to embrace this new broadcasting era. At 1996 small digital satellite dishes hit the market. They become the biggest selling electronic item in history next to the VCR.

Using TV 24H

TV has something for everyone. Idiots, intellectuals, fans of all sorts. Some people are couch potatoes, watch anything just to sit there and be mindless. That's their problem. Children have always needed to be monitored by their parents. If people gotta a mind for it they could figure out the real news even without the internet and there has always been a library.

Is TV bad in and of itself? The researchers aren’t saying that. But we all know that watching television is a solitary, isolating occupation that keeps you sedentary. Sitting in front of the boob tube reduces the time you have available to exercise, interact with your family, read books, and be outdoors. This new research dovetails with other studies, which have linked excessive TV time to obesity and higher rates of cardiovascular disease.

watching too much television can jeopardize your whole family’s health.

This should be a wake-up call to all adults. Stay active. Go outside. Spend time with your spouse and your children with the television off. Read a book and do crossword puzzles to stimulate your imagination and your brain. Reduce your screen time as much as you can.

The National Cancer Institute researchers suggest that watching TV is a public health issue. The price we are paying for our technology-driven lives may be much higher than we previously realized !

DON'T WATCH TV AT ALL !!

The Propaganda TV Machine a.k.a. The Ministry of Truth delivers The Truth from The Government to the people.

At least, that's what they say. In fact, a Propaganda Machine is only employed by The Empire and used to brainwash people into Gullible Lemmings who believe that everything is all right when in fact, it isn't, and that the very people who could help them are their enemies.

Girl Looking TV.

Happy Times:

Do you remember when a telly looked like a real telly? When it was a piece of furniture that you lavished love on, even polished from time to time ?When it was a piece of somewhat at looking in to ?When it was a piece of Highest tech looking inside ? First, this site is a Digital free, HD free, flat panel, HDMI, China, Turks, Afrika free zone. All in all a wealth of vintage information at your finger tips, a one stop unique experience. So step on in, leave the modern throw-away world behind, travel back in time to a vintage world of repair and enjoy.This site has stirred memories about the watching TV's days on a CRT TUBE television......Childhood memories, your parents getting their first colour tv, a b/w or color portable, perhaps memories of renting or buying your first set remote featured, perhaps your days working in the trade, selling or repairing them....... If you enjoyed this site, found its content left you all misty eyed then just talk about it as it would be very welcome............like the time to recover and restore a set ................and happy reminiscing.

Digital TV in Brief.

Digital TV:

Digital television is a hot topic now.If you have looked at television sets at any of the big electronics retailers lately, you know that Digital TV, or DTV, is a BIG deal right now in the U.S. In Europe Digital TV is also a hot topic, because many countries have started terrestrial digital TV broadcasts and plan to end analogue broadcasts after some years (will take 5-10 years). Satellite TV broadcasts have also shifted very much to digital broadcasts.The main advantage if digital broadcasts are that it does not havethe picture quality problems of analogue TVs (it had it's own videoproblems caused by video compression), it allowes putting more TV channels to same medium (TV channel frequencies and satellites) and it allows new services (like HDTV and interactive multimedia). The digital brodcasts are generally designed to use such modulation that the digital data stream (typically around 20-30 Mbit/s) is modulated to the same bandwidth (around 6 MHz) as the analogue TV broadcasts. The used modulation vary between different media, which means thatdifferent modulation techniques are used in terrestrial transmissions, cable TV and satellite. Different modulations are used because of the different characteristics of those transmission medias. There is not on "digital TV", but several different variations of it in use.The basic technology of digital TV, known as MPEG 2 video compressionand MPEG 2 transmission stream format, is same around the world, butis is used somewhat differently in different standards used in differentcountries.

USA uses ACTS Digital Televisio Standard, which standardizes NTSC format transmissions, HDTV transmission, sound formats and data signal modulation in use. The ATSC MPEG-2 formats for DTV, including HDTV, uses 4:2:0 samling for video signal. The US system uses a fixed power and a fixed maximum bitrate, at which some bits are always transmitted. That rate is typically 19.3 Mb/sec.

Europe uses DVB (Digital Video Broadcasting) standard. This standardallows basically normal PAL resolution transmisssion (vasically HDTVcould be added later but is not yet standardized) with several audio formats, digital data rates and digital signal modulation. There are several different variations fo DVB standard for different media:

DVB-T for terrestrial broadcastsDVB-S for satelliteDVB-C for cable TV

Those different DVB versions varyon the data signal modulation methods, error correction and frequency bands used. DVB and option for some interactive extra services, but thestandardization of this is not ready here yet(there are fire different incompatible interactive servicessystems in use in different countries and by different broadcasters).

The process of transmitting digital TV signal is the following: Analog video/audio - digitisation - MPEG compression - Multiplexing ( youcan now call it digital) - Preparation for transmisson - modulation toanalog carrier.Reception process is the following: Demodulation of analogue carrier - Error correction - Demultiplexing - MPEG decompression - DA conversion to get analogue signal (unless you use digital display). The analoguie video signal that gets digitized can be practically from any video source, for example produced with old analogue video production equipment and distributed with a video tape. In high-end system the information is analogue only in the image sensor on the video camera, and from this on the signal gets digitally processed. In many real-life TV production systems the reality is something between those two extremes.

At least in Europe, the signal level requirements for DVB-T are well below the analog requirements, so the transmitter power is much less than on the analog side. In the NorDig recommendation the minimum received signal level for 64QAM, 7/8 code rate with a Rayleigh fading path and 8 dB receiver noise figure would be -64 dBm. With other code rates, modulations and fading mechanisms, the requirement is lower. Many receivers can perform much better at conditions where there is no fading (a quasi error free less than one uncorrected error/hour signal even at 27 dBuV (-82 dBm) with 64QAM and 8 MHz channel width). For analog signals, the recommended level is more than 1 mV (+60 dBuV, -49 dBm). While the ERP can be at least 10 dB lower than analog, the question of power consumption is more complicated, since COFDM with 64QAM carriers require a quite good linearity, which may affect the efficiency and hence power consumption.

Digital TV system in use in USA

The FCC mandate to change our broadcast standards from NTSC analog to ATSC digital broadcasting (DTV) is big bold move, requiring changes in everything from the way the studios shoot video, the format that's transmitted, to the equipment we use to receive and watch broadcastsDTV (digital TV) applies to digital broadcasts in general and to the U.S. ATSC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats. The notation H/DTV is often used to specifically refer to high-definition digital TV. The federal mandate grants the public airwaves to the broadcasters to transmit digital TV in exchange for return of the current analog NTSC spectrum, allowing for a transition period in the interim. At the end of this period scheduled for 2006, broadcasters must be fully converted to the 8VSB broadcast standard. Digital Television ("DTV") is a new broadcast technology that will transform television. The technology of DTV will allows TV broadcasts with movie-quality picture and CD- quality sound and a variety of other enhancements (for example data delivery). With digital television, broadcasters will be able to offer free television of higher resolution and better picture quality than now exists under the current mode of TV transmission. If broadcasters so choose, they can offer what has been called "high definition television" or HDTV, television with theater-quality pictures and CD-quality sound. . Alternatively, a broadcaster can offer several different TV programs at the same time, with pictures and sound quality better than is generally available today. HDTV (high-definition TV) encompasses both analog and digital televisions that have a 16:9 aspect ratio and approximately 5 times the resolution of standard TV (double vertical, double horizontal, wider aspect). High definition is generally defined as any video signal that is at least twice the quality of the current 480i (interlaced) analog broadcast signal. There are 18 approved formats for digital TV broadcasts, but only two (720p/1080i) are proper definition of the term HDTV. The advent of high definition has allowed monitors to read images differently, either in standard interlaced format or progressively. Sets that do not have any decoding capabilities but can display the high-resolution image is often labeled as "HD-Ready" a term that describes 80% or more of the Digital TVs on the market. HDTV displays support digital connections such as HDMI (DVI) and IEEE 1394/FireWire, although standardization is not finished. HDTV in the US is part of the ATSC DTV format. The resolution and frame rates of DTV in the US generally correspond to the ATSC recommendations for SD (640x480 and 704x480 at 24p, 30p, 60p, 60i) and HD (1280x720 at 24p, 20p, and 60p; 1920x1080 at 24p, 30p and 60i). In addition, a broadcaster will be able to simultaneously transmit a variety of other information through a data bitstream to both enhance its TV programs and to provide entirely new services. The technical specifications of USA DTV system is defined in ACTS Digital Television Standards.

Digital TV in Europe

Digital TV brodacasting in Europe is done according to DVB standards. DVB technology has become an integral part of global broadcasting, setting the global standard for satellite, cable and terrestrial transmissions and equipment. There are three versions of DVB in use: DVB-S, DVB-C and DVB-T.DVB-T is a flexible system allowing terrestrial broadcastersto choose from a variety of options to suit their various service environments. This allows the choice between fixed roof-top antenna, portableand even mobile reception of DVB-T services. Broadly speaking the trade-off in one of service bit-rate versus signal robustness.

DVB-T network is very flexible. Having many transmitters all on the same frequency is not a problem for the used COFDM based system. COFDM has been chosen and designed to minimise the effects of multipath in obstructed reception areas. In fact multipath signals can significantly improve the overall received signal with no adverse effects. These properties are particularly valuable for radio cameras and mobile links. DVB-T because of its unique design which allows single frequency networks (SFN). This means that many transmitters along the planned routes can transmit on the same frequency. It is also possible to use simple gap fillers that amplify and retransmit the signal. In-air digital TV broadcasts in Europe use DVB-T. 8 MHz of bandwidth may be used to provide a 24 Mbps digital transmission path using Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation (theoretical maximum 31.67 Mbits for 8 MHz bandwidth). In cases where less bandwidth is available (6 or 7 MHz), the data rate is somewhat lower (around 20 Mbit/s).

DVB-C does the same function as DVB-T, but the modulation used in this system is optimized to operate well in cable TV networks. The modulation used in DVB-C is QAM. Systems from 16-QAM up to 256-QAM can be used, but the system centres on 64-QAM, in which an 8MHz channel can accommodate a physical payload of about 38 Mbit/s. Digital cable TV in Europe uses DVB-C. The DVB standard for the cable return path has been developed jointly with DAVIC, the Digital Audio Visual Council. The specification uses Quadrature Phase Shift Keying (QPSK) modulation in a 200kHz, 1MHz or 2MHz channel to provide a return path for interactive services (from the user to the service provider) of up to about 3Mbit/s. The path to the user may be either in-band (embedded in the MPEG-2 Transport Stream in the DVB-C channel) or out-of-band (on a separate 1 or 2MHz frequency band).

DVB-S is the satellite version of DVB. Satellite transmission has lead the way in delivering digital TV to viewers. Established in 1995, the satellite standard DVB-S is the oldest DVB standard, used on all six major continents. QPSK modulation system is used, with channel coding optimised to the error characteristics of the channel. A typical satellite channel has 36 MHz bandwidth, which may support transmission at up to 38 Mbps (assuming delivery to a 0.5m receiving antenna) using Quadrature Phase Shift Keying (QPSK) modulation. 16 bytes of Reed Solomon (RS) coding are added to each 188 byte transport packet to provide Forward Error Correction (FEC) using a RS(204,188,8) code. For the satellite transmission, the resultant bit stream is then interleaved and convolutional coding is applied.

The core of the DVB digital data stream isthe standard MPEG-2 "data container",which holds the broadcast and service information.This flexible "carry-all" can containanything that can be digitised, includingmultimedia data. The MPEG-2 standards define how to format the various component parts of a multimedia programme (which may consist of: MPEG-2 compressed video, compressed audio, control data and/or user data). It also defines how these components are combined into a single synchronous transmission bit stream. The process of combining the steams is known as multiplexing. The multiplexed stream may be transmitted over a variety of links, standards / products.Each MPEG-2 MPTS multiplex carries a number of streams which in combination deliver the required services. A typical data rate of such multiplex is around 24 Mbps for terrestrial brodcasts.

European DVB systems currently transmit only standard definition TV signals and set top boxes also handle only normal TV resolution. It would be possible to transmit HDTV signals on DVB data stream, but those broadcasts have not yet started in any wide scale. There is one satellite broadcater that broadcasts HDTV DVB signals in Europe (some cable TV operators carry that signal on their cable).

Many DVB-T integrated TV sets, and some set top boxes, in the Europe come with a Common Interface slot - which is pretty much the same form-factor as a PC Card (aka PCMCIA) used in PC laptops. This CI slot accepts a Conditional Access Module, in the same way that DVB-S receivers do, which implements at least one (some can do more than one) decryption algorithm. This CAM may also, itself, have a smart card slot to accept a consumer subscription card to authorise decryption - you plug your smartcard into your CAM and your CAM into the CI slot in your receiver/IDTV. Some DVB receivers have an integrated CAM (in the case of some receivers this is implemented purely in software, with no extra hardware required) rather than a CI slot to plug in a 3rd party device. With these type of receivers you just plug in the smart card and don't have to worry about CI slots and buying CAMs. So there is an interface standard for DVB - but different broadcasters can chose different encryption schemes, requiring different CAMs for decryption.

DVB Standards and related documents are published by the European Telecommunications Standards Institute (ETSI). These include a large number of standards and technical notes to complement the MPEG-2 standards defined by the ISO.

There are few different standard how interactive TV functionaly is implemented in DVB-systems in use in differenct countries. DVB-MHP is one gaining some acceptance. Multimedia Home Platform (MHP) is the open middleware system designed by the DVB Project (www.dvb.org).